CN119643985B - Spectroscopy method for measuring built-in electric field intensity on gallium nitride crystal surface - Google Patents
Spectroscopy method for measuring built-in electric field intensity on gallium nitride crystal surfaceInfo
- Publication number
- CN119643985B CN119643985B CN202411721418.1A CN202411721418A CN119643985B CN 119643985 B CN119643985 B CN 119643985B CN 202411721418 A CN202411721418 A CN 202411721418A CN 119643985 B CN119643985 B CN 119643985B
- Authority
- CN
- China
- Prior art keywords
- electric field
- built
- gallium nitride
- field strength
- measuring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Landscapes
- Testing Or Measuring Of Semiconductors Or The Like (AREA)
Abstract
本发明公开了一种测量氮化镓晶体表面内建电场强度的光谱学方法。利用飞秒瞬态反射光谱技术，研究了氮化镓晶体表面内建电场中载流子动力学过程，实现了其表面内建电场强度的测量，包括以下步骤：搭建泵浦‑探测瞬态反射光路，测试氮化镓外延表面的瞬态反射光谱，通过改变不同的激发波长测试不同初始载流子分布下的表面内建电场强度变化随时间的演化过程，通过拟合载流子扩散‑漂移耦合模型得到氮化镓表面内建电场的耗尽层厚度，计算得到内建电场的强度。本发明作为一种超快时间分辨的泵浦‑探测光谱技术，适合用于研究重掺杂氮化镓表面载流子动力学过程，为优化GaN基光电器件的性能提供理论指导。
The present invention discloses a spectroscopic method for measuring the built-in electric field strength on the surface of a gallium nitride crystal. Using femtosecond transient reflectance spectroscopy, the carrier dynamics in the built-in electric field on the surface of a gallium nitride crystal are studied, and the built-in electric field strength is measured. The method includes the following steps: establishing a pump-probe transient reflectance optical path, testing the transient reflectance spectrum of the gallium nitride epitaxial surface, measuring the temporal evolution of the built-in electric field strength under different initial carrier distributions by varying the excitation wavelength, obtaining the depletion layer thickness of the built-in electric field on the gallium nitride surface by fitting a carrier diffusion-drift coupling model, and calculating the built-in electric field strength. As an ultrafast time-resolved pump-probe spectroscopy technique, the present invention is suitable for studying the surface carrier dynamics of heavily doped gallium nitride, providing theoretical guidance for optimizing the performance of GaN-based optoelectronic devices.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a spectroscopy method for measuring the built-in electric field intensity on the surface of a gallium nitride crystal.
Background
In semiconductor materials and devices, built-in electric field (build-IN ELECTRIC FIELD) is an important factor affecting their electronic and optical properties. Built-in electric fields are typically present at pn junctions, heterojunctions, quantum wells, and material surfaces and interfaces, caused by charge distribution non-uniformity or polarization effects. Accurate measurement and understanding of the strength of built-in electric fields is critical to regulating the electrical, optical and thermal properties of semiconductor devices, especially in microelectronic and optoelectronic devices such as field effect transistors, diodes, light emitting diodes and solar cells. Gallium nitride (GaN) and its related materials (e.g., inGaN, alGaN) are important wide bandgap semiconductors that are widely used in the fabrication of high power, high frequency electronic devices and high efficiency light emitting devices (e.g., LEDs and lasers). GaN materials have strong spontaneous and piezoelectric polarization effects that result in strong built-in electric fields inside and on the surface of the material. The built-in electric field has a significant impact on carrier transport, band structure and optical performance of GaN-based devices. Therefore, developing an effective experimental method to measure and study the built-in electric field of GaN surface is of great importance for understanding and optimizing device performance.
The ultra-fast transient reflection spectrum is an emerging optical measurement technology, and the technology irradiates a sample through ultra-short pulse laser (usually in the femtosecond order) and measures the change of the reflection spectrum in real time, so that the non-contact dynamic measurement can be carried out on the built-in electric field of the semiconductor material, and a powerful means for researching the evolution of the electric field on the surface of the semiconductor is provided. Therefore, the invention aims to develop an ultrafast transient reflection spectrum method for measuring the built-in electric field intensity on the surface of the gallium nitride crystal, which is used for researching the built-in electric field intensity on the surface of the gallium nitride crystal.
Disclosure of Invention
The invention aims to solve the technical problem of providing an ultrafast transient reflection spectrum method for measuring the built-in electric field intensity on the surface of a gallium nitride crystal, which adopts a pumping-detection technology to regulate and control the initial carrier concentration distribution by changing the wavelength of pumping light, uses detection light to monitor the evolution of reflectivity in real time, and fits a carrier diffusion-drift coupling model to obtain the built-in electric field intensity.
The technical scheme adopted by the invention for realizing the purpose is that the spectroscopy method for measuring the built-in electric field intensity on the surface of the gallium nitride crystal comprises the following steps:
Exciting electrons to a conduction band by adopting single photon excitation or two photon excitation through a laser, and leaving holes in a valence band;
adjusting the incidence angle of the detection light on the gallium nitride film sample, and enabling the pumping light emitted by the optical parametric amplifier to be incident on the front surface of the gallium nitride film sample;
collecting detection light reflected by the surface of a gallium nitride film sample, and testing transient absorption spectrum;
Acquiring delta R/R data according to the spectrum information, wherein R represents the detection light reflectivity excited by the pump light, delta R represents the difference value between the detection light reflectivity excited by the pump light and the detection light reflectivity excited by the non-pump light;
And obtaining the width of the depletion layer by fitting according to the delta R/R data, and obtaining the built-in electric field intensity according to the width of the depletion layer.
The wavelength of the detection light is 340 nm-800 nm.
The incidence angle of the adjustment detection light on the gallium nitride film sample is 45 degrees.
The pump light emitted by the optical parametric amplifier is incident on the front surface of the gallium nitride film sample, and the incident angle is 0-10 degrees.
The pump light excitation wavelengths of 260nm and 400nm were varied to test the transient reflectance spectrum.
And acquiring delta R/R data, and fitting experimental data by utilizing a carrier drift-diffusion model to obtain the width of the depletion layer of the built-in electric field.
The built-in electric field strength is obtained according to the width of the depletion layer and is obtained by the following formula:
Wherein F is the built-in electric field strength, W 0 is the depletion layer width, q is the electron charge amount, N D is the doping concentration, ε is the relative permittivity, ε 0 is the vacuum permittivity.
The invention has the following beneficial effects and advantages:
1. transient reflectance spectroscopy is an optical method, so that measurements can be made without touching the sample, avoiding interference that may be introduced by electrode contact in conventional electrical methods. Such non-contact measurements are particularly suitable for surface sensitive or vulnerable semiconductor materials.
2. Conventional electrical measurements sometimes require the preparation of electrodes on the sample or the introduction of an externally applied electric field, which may have a certain physical or chemical effect on the surface of the material. Whereas transient reflectance spectroscopy is completely non-invasive and does not damage the sample, it is particularly suitable for measuring fragile or difficult to handle materials.
3. The transient reflection spectrum can be utilized to realize the spatial resolution of micron-scale or even nanometer-scale through optical focusing, so that the built-in electric field of the local area of the semiconductor surface is measured. In contrast, conventional electrical methods often have difficulty achieving such high spatial resolution.
Drawings
Fig. 1 is a constructed light path diagram of an ultrafast transient reflectance spectrum.
FIG. 2 is a graph of a transient reflectance time-sharing spectrum of GaN epitaxy in an example.
Fig. 3 is a graph of carrier dynamics of gallium nitride epitaxy in an example under excitation at different excitation wavelengths.
Fig. 4 is a flow chart of the method of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
The invention discloses a spectroscopy method for measuring the built-in electric field intensity on the surface of gallium nitride crystal. The method comprises the steps of constructing a pumping-detecting transient reflection light path, testing transient reflection spectrum of the gallium nitride epitaxial surface, testing the evolution process of the change of the intensity of the built-in electric field on the surface under different initial carrier distribution along with time by changing different excitation wavelengths, obtaining the thickness of a depletion layer of the built-in electric field on the gallium nitride surface by fitting a carrier diffusion-drift coupling model, and calculating the intensity of the built-in electric field. The invention is used as an ultrafast time-resolved pump-detection spectrum technology, is suitable for researching the dynamic process of the carrier on the surface of the heavily doped gallium nitride, and provides theoretical guidance for optimizing the performance of a GaN-based photoelectric device.
As shown in fig. 4, the present invention includes the steps of:
(1) The system mainly comprises three components, namely a femtosecond titanium precious stone laser system (800 nm,35fs,1 kHz), an Optical Parametric Amplifier (OPA) and a transient spectrometer. The TOPAS OPA is mainly used for generating pump light (240 nm-2600 nm) with adjustable wavelength, and the transient spectrometer comprises a time Delay control device (Variable Delay), a calcium fluoride crystal window, a chopper, a detector and the like. The system can realize time resolution of 35fs, the maximum delay time is 8ns, and the wavelength of detection light (white light) can cover 340 nm-800 nm. The incidence angle of the detection light on the film sample is regulated to be about 45 degrees, the detection light reflected by the surface of the sample enters the optical fiber spectrometer, and the pumping light is incident on the front surface of the film sample, and the incidence angle is 0-10 degrees.
(2) And (3) testing the gallium nitride epitaxial transient reflection spectrum, wherein a sample is a gallium nitride epitaxial wafer with a Si doped (0001) crystal face, and the thickness is 4.5 microns. And respectively adopting single photon excitation and two photon excitation to excite electrons into a conduction band, wherein the wavelength of pumping light is 260nm and 400nm, the wavelength range of detection light is 340nm-800nm, and collecting detection light through an ultraviolet detector to test transient absorption spectrum.
(4) And calculating the built-in electric field intensity of gallium nitride, namely, drifting, diffusing and compounding carriers on the surface of the semiconductor. Drift and diffusion will result in an enhancement of the modulated electric field (the observed signal rising from 0 to-1 in fig. 3), while carrier recombination will result in a reduction of the photogenerated electric field (the observed signal decaying from-1 to 0). It is assumed here that carriers located in the depletion region are mainly drifting, while carriers located outside the depletion region (neutral region) are mainly diffusing. Carriers residing in the neutral region may diffuse into the depletion region or may diffuse toward the bulk phase driven by a concentration gradient.
(5) And acquiring delta R/R data, and fitting the delta R/R data acquired by experiments with the data of delta R/R along with delay time by using a carrier drift-diffusion coupling model to obtain the width of the depletion layer. Wherein R represents the detection light reflectance of the sample surface not excited by the pump light, and Δr represents the difference between the detection light reflectance excited by the pump light and the detection light reflectance not excited by the pump light.
The change over time of the concentration profile of carriers in the neutral region of the GaN thin film can be expressed as:
Here, N represents carrier concentration, D is minority carrier (hole) diffusion coefficient, and τ is bulk recombination lifetime. t is the delay time after the sample is excited and x is the depth from the sample surface.
For n-doped GaN, there is an upward band bending of the surface, photo-generated holes diffuse into the depletion layer, then the holes are swept to the surface under the action of the built-in electric field, and photo-generated electrons are swept to the surface of the neutral region under the action of the built-in electric field, then diffuse into the bulk phase. The final transient electric field strength depends on the number of photo-generated holes from the bulk phase to the depletion layer. One common approach is to assume that a virtual boundary surface separates the depletion region from the neutral region, and that the carrier flux at that boundary is characterized by the charge carrier rate, resulting in the boundary condition that the carrier flux needs to meet as follows:
Here, W 0 is the depletion layer width, S V is the hole thermal velocity of the depletion layer virtual boundary, and J represents the carrier flux. The final transient reflection signal is proportional to the carrier concentration, i.e
The absorption coefficient is different for different excitation wavelengths, so the initial carrier concentration distribution is also different, and the initial carrier concentration distribution is expressed as
N(x, 0) =N0·exp(-αx) (5)
Where α is the absorption coefficient, and N 0 is the carrier concentration at time t=0. Fitting TR dynamics can result in depletion layer width and minority carrier (hole) diffusion coefficient D using the carrier drift-diffusion coupling model consisting of equations (1) - (5).
(6) The built-in electric field intensity is calculated as follows:
Where q is the electron charge, N D is the doping concentration, ε is the relative permittivity, ε 0 is the vacuum permittivity.
Examples:
The present embodiment describes a method for measuring the intensity of a built-in electric field on the surface of gallium nitride epitaxy, using Si-doped gallium nitride epitaxy of (0001) crystal plane grown on a sapphire substrate as an exemplary object, comprising the steps of:
1. an ultrafast time-resolved transient reflection spectrum optical path based on a pump-detection technology is built, and specific details are shown in fig. 1.
The angle of incidence of the probe light on the GaN film sample is adjusted to be about 45 degrees, and the angle of the reflecting mirror is adjusted to enable the pump light to vertically enter the surface of the GaN film sample, wherein the incidence angle is 0 degree.
2. The band gap of gallium nitride is 3.4eV, 260nm is selected as excitation light (photon energy is about 4.8 eV), valence band electrons are excited to a conduction band by a single photon excitation technology, holes are reserved in the valence band, and super-continuous white light is used as detection light to detect the change of an excited state carrier in real time. As shown in fig. 2, a spectrum oscillation phenomenon can be seen above the band gap, which is FKO oscillations caused by the built-in electric field, when the spectrum is time-division spectrum of the GaN transient reflection spectrum.
3. The kinetics at 366nm were extracted using 260nm and 400nm as pump light, respectively, as shown in FIG. 3. And (3) writing a fitting program by using formulas (1), (2), (3), (4) and (5), and fitting the experimental data, so that the experimental data can be found to completely coincide with a fitting curve. Wherein the fixed first-order attenuation rate is 1E+9s -1, the GaN epitaxial thickness is 2 μm, the Sv is 1E+7cm/s, the surface recombination rate is 1000cm/s, and the final fitting result is that the diffusion coefficient D is 0.466cm 2/s and the depletion layer thickness W 0 is 31.0nm.
4. Calculating the built-in electric field intensity of the GaN surface according to the formula (6), wherein q is 1.6X10 -19C,W0 to 31.0nm, N D is 1×10 18cm-3, epsilon is 9.5, epsilon 0 is 8.85×10 -12 F/m, and the built-in electric field intensity is 3.1X10 4 V/cm.
Claims (7)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202411721418.1A CN119643985B (en) | 2024-11-28 | 2024-11-28 | Spectroscopy method for measuring built-in electric field intensity on gallium nitride crystal surface |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202411721418.1A CN119643985B (en) | 2024-11-28 | 2024-11-28 | Spectroscopy method for measuring built-in electric field intensity on gallium nitride crystal surface |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN119643985A CN119643985A (en) | 2025-03-18 |
| CN119643985B true CN119643985B (en) | 2025-10-17 |
Family
ID=94945265
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202411721418.1A Active CN119643985B (en) | 2024-11-28 | 2024-11-28 | Spectroscopy method for measuring built-in electric field intensity on gallium nitride crystal surface |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN119643985B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101221203A (en) * | 2007-12-21 | 2008-07-16 | 中国科学院上海技术物理研究所 | A method for detecting harmful interface charge of mercury cadmium telluride thin film photovoltaic devices |
| CN116263403A (en) * | 2021-12-13 | 2023-06-16 | 中国科学院大连化学物理研究所 | Measurement method of back excitation-front detection TR and film longitudinal diffusion coefficient |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05173200A (en) * | 1990-07-02 | 1993-07-13 | Canon Inc | Method and apparatus for modulating light using semiconductor device having quantum well structure |
| JPH10199949A (en) * | 1997-01-10 | 1998-07-31 | Nippon Telegr & Teleph Corp <Ntt> | Semiconductor crystal measurement method |
| JP4031712B2 (en) * | 2003-01-17 | 2008-01-09 | 三菱電機株式会社 | Spectroscopic measurement method and spectroscopic measurement apparatus for semiconductor multilayer film |
| JP4441381B2 (en) * | 2004-10-29 | 2010-03-31 | 三菱電機株式会社 | Method for measuring surface carrier recombination velocity |
| JP5006331B2 (en) * | 2005-10-27 | 2012-08-22 | ザイトロニクス・コーポレーション | Method for characterization of light reflection of strain and active dopants in semiconductor structures |
| US8093139B2 (en) * | 2008-12-11 | 2012-01-10 | Anteos, Inc. | Method for fabrication of aligned nanowire structures in semiconductor materials for electronic, optoelectronic, photonic and plasmonic devices |
| CN117405608A (en) * | 2022-12-15 | 2024-01-16 | 中国科学院大连化学物理研究所 | A spectroscopic method for measuring electron or hole diffusion coefficients |
-
2024
- 2024-11-28 CN CN202411721418.1A patent/CN119643985B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101221203A (en) * | 2007-12-21 | 2008-07-16 | 中国科学院上海技术物理研究所 | A method for detecting harmful interface charge of mercury cadmium telluride thin film photovoltaic devices |
| CN116263403A (en) * | 2021-12-13 | 2023-06-16 | 中国科学院大连化学物理研究所 | Measurement method of back excitation-front detection TR and film longitudinal diffusion coefficient |
Also Published As
| Publication number | Publication date |
|---|---|
| CN119643985A (en) | 2025-03-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Kuciauskas et al. | Minority carrier lifetime analysis in the bulk of thin-film absorbers using subbandgap (two-photon) excitation | |
| CN100511623C (en) | Method for measuring semiconductor doping concentration | |
| US8809092B2 (en) | Generating and detecting radiation | |
| Berini et al. | Thin Au surface plasmon waveguide Schottky detectors on p-Si | |
| CN108956537A (en) | A kind of Superfast time resolution transient state reflecting spectrograph | |
| CN111880072A (en) | Method for characterizing 4H-SiC electrical properties by Raman spectrum based on photon-generated carrier effect | |
| US9404874B2 (en) | Inspection apparatus and inspection method | |
| CN115728250B (en) | Semiconductor carrier dynamics test instrument and test method | |
| Dugar et al. | Carrier relaxation dynamics in defect states of epitaxial GaN/AlN/Si using ultrafast transient absorption spectroscopy | |
| CN119643985B (en) | Spectroscopy method for measuring built-in electric field intensity on gallium nitride crystal surface | |
| Gerber et al. | A simple method for extraction of multiple quantum well absorption coefficient from reflectance and transmittance measurements | |
| CN119290848B (en) | Gallium-rich defect detection method for gallium nitride device based on second harmonic enhancement | |
| Nwabunwanne | Design, fabrication and characterization of efficient and ultrafast ultraviolet photodiodes based on aluminum gallium nitride/gallium nitride heterostructures | |
| CN101467022A (en) | Method of phot0-reflectance characterization of strain and active dopant in semiconductor structures | |
| Recht et al. | Contactless microwave measurements of photoconductivity in silicon hyperdoped with chalcogens | |
| CN208224427U (en) | The measuring device of minority carrier Subspace Distribution in low-gap semiconductor | |
| Collins | Dilute Nitride GaInNAsSb for Next Generation Optical Communications | |
| Klimov et al. | Generation of THz Radiation by (100),(110), and (111) A-Oriented Multiple Pseudomorphic InGaAs/GaAs Quantum Wells and Photoconductive Antennas | |
| Mandelis | Photo-carrier radiometry of semiconductors: A novel powerful optoelectronic diffusion-wave technique for silicon process non-destructive evaluation | |
| Yu et al. | Measurement of the Al mole fraction of bulk AlGaN and AlGaN/GaN heterostructure by photoconductance method | |
| TWI420094B (en) | Method of photo-reflectance characterization of strain and active dopant in semiconductor structures | |
| WO2010115994A1 (en) | Determining active doping profiles in semiconductor structures | |
| González-Colsa et al. | Gradient-free temperature control over micrometric areas for thermoplasmonic applications in micro-and nano-devices | |
| CN101201324A (en) | Detection Method of Peak Response Wavelength of Gallium Arsenide/AlGaAs Infrared Quantum Well Material | |
| Xiao et al. | Correction to Optical and Electronic Properties of Colloidal CdSe Quantum Rings |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |