CN102735665B - Device for measuring Schottky barrier height and method thereof - Google Patents
Device for measuring Schottky barrier height and method thereof Download PDFInfo
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- CN102735665B CN102735665B CN201210209958.2A CN201210209958A CN102735665B CN 102735665 B CN102735665 B CN 102735665B CN 201210209958 A CN201210209958 A CN 201210209958A CN 102735665 B CN102735665 B CN 102735665B
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Abstract
The invention discloses a device for measuring Schottky barrier height and a method thereof. The device comprises a light source, a photointerrupter, a first lens, a sample to be measured, a first source-meter, a second lens, a monochromator, a detector, a lock-in amplifier, a second source-meter and a computer. The computer controls the monochromator, the first source-meter and the second source-meter. Therefore, the first source-meter scans the offset voltage of the Schottky barrier sample, and the Schottky barrier height value is determined from photoluminescence intensity of selected wavelength in the obtained Schottky barrier area and an offset voltage variation curve. By the utilization of the invention, as the Schottky barrier height is obtained from the variation characteristic of the measured photoluminescence intensity with the variation of the offset voltage, the influence of electric leakage effect caused by a device edge in parallel with a resistor on the measurement of the Schottky barrier height is avoided. The device provided by the invention has advantages of high measurement precision, good consistency, non-destructiveness and the like.
Description
Technical field
The present invention relates to optical semiconductor electro-technical field, relate to a kind of apparatus and method of measuring semiconductor schottky barrier height.
Background technology
Metal-involuntary (or light) doping direct band-gap semicondictor material-homogeneity heavy doping direct band-gap semicondictor material contact structures reach after balance, there is unified Fermi level, three's Fermi level is in same level of energy, total Built-in potential V of this structure
biequal the work function Φ of metal
mdeduct the work function Φ of heavy doping GaN
n,
V
bi＝Φ
m-Φ
N
Schottky barrier height φ after the contact of metal-involuntary (or light) doping direct band-gap semicondictor material
bequal the work function Φ of metal
mdeduct the electron affinity χ of direct band-gap semicondictor material
s, have:
φ
B＝Φ
m-χ
s
＝Φ
m-Φ
N+k*T*ln(N
c/n
N)
＝V
bi+k*T*ln(N
c/n
N)
N in formula
cthe available state density in direct band-gap semicondictor material conduction band, n
nit is the carrier concentration of heavy doping direct band-gap semicondictor material.K is this graceful constant of bohr, and T is absolute temperature.Generalized case, n
napproach and be equal to or greater than N
c, k*T*ln (N
c/ n
n) < < φ
b, as counterweight Doped GaN material under room temperature, n
n=2*10
18* cm
-3, k*T=0.0259eV, N
c=2.2*10
18cm
-3, k*T*ln (Nc/nN)=0.0025eV.Therefore have:
For metal-involuntary (or light) doping direct band-gap semicondictor material-homogeneity heavy doping direct band-gap semicondictor material contact structures, the schottky barrier height φ between metal-involuntary (or light) doping direct band-gap semicondictor material
bbe approximately equal to total Built-in potential V of metal-involuntary (or light) doping direct band-gap semicondictor material-homogeneity heavy doping direct band-gap semicondictor material contact structures
bi.
Common a part of Schottky barrier photodetector is metal-involuntary (or light) doping direct band-gap semicondictor material-homogeneity heavy doping direct band-gap semicondictor material contact structures.Light, in the time irradiating Schottky barrier photodetector depletion region, can produce photo-generated carrier (electronics, hole), and under the effect of depletion region electric field, electronics, hole are swept out respectively depletion region, forms photocurrent.The width of depletion region changes with the variation of its applying bias voltage.The width that is depletion region increases along with the increase of reverse biased, reduces along with the increase of forward bias.In the time that forward bias (unit: V) equals schottky barrier height (unit: eV), the semiconductor energy gap in Schottky barrier district becomes flat rubber belting, and depletion region built in field intensity becomes 0.At the width of depletion region from the process of 0 broadening, the photocathode that light causes in the time irradiating Schottky barrier region can increase and reduce along with width of depletion region, this is the increase due to width of depletion region, Electric Field Distribution space enlargement, in built in field direction, in depletion region, the electric field intensity of relevant position increases simultaneously, accelerated separation and the sweep-out effect of photo-generated carrier, reduced the probability of radiation recombination, photocathode reduces.In the time that forward bias is more than or equal to schottky barrier height, depletion region built in field intensity is 0, the separation of photo-generated carrier and sweep-out effect change very little with the increase of forward voltage, radiation recombination probability also changes very little with the increase of forward voltage, photocathode changes very little with the increase of forward voltage.Consider that Schottky barrier sample is in the time of forward bias voltage state, having forward current to inject conventionally can luminescence phenomenon yet.Therefore, in forward bias voltage, since 0 process increasing, width of depletion region narrows, and depletion region built in field intensity diminishes until 0, and the photo-generated carrier that illumination produces is because depletion region narrows and built in field weakened, and separation effect dies down, until stable; Corresponding photocathode grow gradually, until intensity stabilization; It is schottky barrier height (unit: eV) that photocathode starts to become forward voltage (unit: V) corresponding while stablizing.According to this physical phenomenon, the photocathode of measuring the Schottky barrier region of sample just can obtain the schottky barrier height of sample with the change curve of bias voltage.
The apparatus and method of measurement schottky barrier height provided by the invention, have realized measurement Schottky barrier region light change in fluorescence characteristic and utilize this feature measurement schottky barrier height under electric field.Measure light change in fluorescence characteristic and the schottky barrier height of Schottky barrier region under electric field by this proving installation and method, for material behavior, the device property of further analyzing Schottky barrier sample provide a kind of testing tool and method.
Summary of the invention
(1) technical matters that will solve
In view of this, fundamental purpose of the present invention is to provide a kind of apparatus and method of measuring schottky barrier height, measures Schottky barrier region light change in fluorescence characteristic and utilize this feature measurement schottky barrier height under electric field to realize.
(2) technical scheme
For achieving the above object, the invention provides a kind of device of measuring schottky barrier height, comprising:
One light source, for the optical signal source of this device is provided, to excite the Schottky barrier region of testing sample, sends light fluorescence;
One optical chopper, for the light beam copped wave in the Schottky barrier region to inciding testing sample, synchronization output signal is received the reference signal input end of lock-in amplifier;
One first lens, is positioned at before testing sample, converges light beam that optical signal source sends in the Schottky barrier region of testing sample;
One testing sample, is placed on sample stage, and Schottky barrier area surfaces and the incident beam of this testing sample are angled, the light beam of Schottky barrier area surfaces reflection is not entered and converge the second lens and spectrometer;
One first source table, is connected with testing sample, for plus or minus bias voltage is provided to testing sample, testing sample is carried out voltage scanning and measures the electric current under corresponding bias voltage;
One second lens, are placed on the front perpendicular to the Schottky barrier area surfaces direction of testing sample, converge the light fluorescence sending in Schottky barrier region, incide monochromator thereafter;
One monochromator, for receiving the light fluorescence sending in Schottky barrier region, carries out wavelength to light fluorescence and selectes or scan, and incides detector thereafter;
One detector, for measuring the light intensity of the light fluorescence sending under the different bias voltages in Schottky barrier region under the selected wavelength of monochromator;
One lock-in amplifier, the signal input part of lock-in amplifier is connected with the signal output part of detector, for measuring the signal of detector output terminal;
One second source table, is connected with the output terminal of lock-in amplifier, for measuring the output end voltage of lock-in amplifier; And
One computing machine, be used for controlling monochromator, the first source table and the second source table, realize the bias voltage scanning of the first source table to Schottky barrier sample, in photocathode from the selected wavelength in Schottky barrier region obtaining and bias voltage (dividing potential drop in deduction resistance in series, lower same) change curve, determine schottky barrier height numerical value.
In such scheme, described computing machine receives the selected wavelength of the monochromator sending under different bias voltages in Schottky barrier region, and (photon energy is near energy gap, photocathode data down together), carry out corresponding signal data processing, obtain photocathode and bias voltage change curve under the selected wavelength in Schottky barrier region; Be less than within the scope of schottky barrier height value when forward bias voltage is in, photocathode increases along with the increase of forward bias; Be equal to or greater than within the scope of schottky barrier height value when forward bias voltage is in, photocathode changes not obvious along with forward voltage increase, and intensity is more stable; Therefore, in the Schottky barrier area light fluorescence intensity obtaining and bias voltage change curve, when photocathode starts to stablize with forward voltage increase under forward bias voltage, corresponding bias voltage numerical value is exactly schottky barrier height numerical value, wherein the unit of bias voltage numerical value is V, and the unit of schottky barrier height numerical value is eV.
In such scheme, described computer control monochromator carries out length scanning or selected a certain outgoing wavelength to light fluorescence; Computer control the first source table and the second source table, the first source table is implemented the bias voltage scanning to Schottky barrier sample and is measured the electric current under corresponding bias voltage, the second source table receives the glimmering light intensity of light under corresponding bias voltage, computing machine carries out corresponding signal processing, obtains Schottky barrier area light fluorescence intensity and biasing bias variations curve.
In such scheme, described light source is helium cadmium laser, or is a kind of light source in xenon lamp, tungsten lamp and deuterium lamp light through the selected wavelength of monochromator, is wherein greater than the energy gap of testing sample through the photon energy of the light of the selected wavelength of monochromator.
In such scheme, the light that described first lens sends light source converges to the Schottky barrier region of testing sample, and the spot size while inciding schottky area is less than Schottky barrier area surfaces.
In such scheme, described testing sample surface forms an angle with unpolarized light beam, and the folded light beam on incident light and testing sample surface has angle, folded light beam can not be incided and converge in second lens and monochromator of light fluorescence.
In such scheme, described testing sample is the Schottky barrier sample that direct band-gap semicondictor material is made, and photon energy is greater than its Schottky barrier region of light beam irradiates of its energy gap can send light fluorescence.
In such scheme, described the first source table provides plus or minus bias voltage to testing sample, and testing sample is carried out voltage scanning and measures the electric current under corresponding bias voltage.
In such scheme, described in converge light fluorescence the second lens the light fluorescence emitting from testing sample is converged, incide the entrance slit of monochromator thereafter.
In such scheme, described monochromator receives the light fluorescence that send in Schottky barrier region, and light fluorescence is carried out to length scanning or selected a certain wavelength, incides detector thereafter.
In such scheme, described detector is photodiode or photomultiplier, for measuring the strength characteristics of light fluorescence.
For achieving the above object, the present invention also provides a kind of method of measuring schottky barrier height, comprising:
Step 1: the laser beam that light source sends, after chopper copped wave, is focused on by first lens on the Schottky barrier region of testing sample, and the spot size while inciding schottky area is less than Schottky barrier area surfaces; The synchronization output signal of optical chopper is received the reference signal input end of lock-in amplifier;
Step 2: adjust testing sample and sample stage, Schottky barrier area surfaces and incident beam are angled, does not enter light beam that Schottky barrier area surfaces reflects and converges the second lens and spectrometer;
Step 3: the first source table is connected with testing sample, provides plus or minus bias voltage to testing sample, carries out voltage scanning and measures the electric current under corresponding bias voltage testing sample;
Step 4: the second lens are placed on the front perpendicular to the Schottky barrier area surfaces direction of testing sample, converge the light fluorescence sending in Schottky barrier region, incide the entrance slit of monochromator thereafter;
Step 5: the light fluorescence that send in the Schottky barrier region of monochromator reception testing sample, light fluorescence is carried out to wavelength and select or scan, incide detector thereafter;
Step 6: the light intensity of the light fluorescence sending under the different bias voltages in Schottky barrier region of detector measurement sample under the selected wavelength of monochromator;
Step 7: the signal input part of lock-in amplifier is connected with the signal output part of detector, the signal of measurement detector output terminal;
Step 8: the second source table is connected with the output terminal of lock-in amplifier, measures the output end voltage of lock-in amplifier;
Step 9: computer control monochromator, the first source table and the second source table, realize the bias voltage scanning of the first source table to sample, computing machine receives the photocathode data that send under different bias voltages in Schottky barrier region, carry out corresponding signal data processing, photocathode and the bias voltage change curve under wavelength selected in the Schottky barrier region that obtains testing sample, obtained the schottky barrier height numerical value of testing sample by this curve.
(3) beneficial effect
Can find out from technique scheme, the present invention has following beneficial effect:
The device and method of measurement schottky barrier height provided by the invention, because schottky barrier height is to obtain the wide variety characteristic with bias voltage change depletion region from photocathode, the impact of having avoided device edge parallel resistance leakage effect to measure schottky barrier height, so measuring accuracy is high, high conformity, has non-destructive advantage.
Accompanying drawing explanation
For further illustrating concrete technology contents of the present invention, describe in detail thereafter below in conjunction with embodiment and accompanying drawing, wherein
Fig. 1 is the schematic diagram according to the device of the measurement schottky barrier height of the embodiment of the present invention;
Fig. 2 is according to the not Doped GaN (Qundoped) of the embodiment of the present invention, gently mixes the change curve (monochromator is selected outgoing wavelength: 363.2nm) of silicon GaN (Qdoped) Schottky barrier photodetector photocathode and bias voltage.
Fig. 3 is according to the not Doped GaN (Iundoped) of the embodiment of the present invention, gently mixes electric current and bias voltage (I-V) curve of silicon GaN (Idoped) Schottky barrier photodetector.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
As shown in Figure 1, Fig. 1 is that this device comprises according to the schematic diagram of the device of the measurement schottky barrier height of the embodiment of the present invention:
One light source 1, this light source provides the optical signal source of test macro, is used for exciting the Schottky barrier region of Schottky sample 4, sends light fluorescence.
One optical chopper 2, this chopper is to carrying out copped wave by light source 1 light beam that incides Schottky barrier region out.The synchronization output signal of optical chopper 2 is received the reference signal input end of lock-in amplifier 9.
One first lens 3, these lens are placed on before Schottky barrier sample 4, converge light beam that optical signal source 1 sends in the Schottky barrier region of Schottky barrier sample 4 to be measured; Spot size while inciding schottky area is less than Schottky barrier area surfaces;
One Schottky barrier sample 4 to be measured, is placed on sample stage, and Schottky barrier area surfaces and the incident beam of this sample are angled, the light beam of Schottky barrier area surfaces reflection is not entered and converge the second lens 6 and spectrometer 7.
One first source table 5 is connected with Schottky barrier sample 4, offers the plus or minus bias voltage of Schottky barrier sample 4 to be measured, and Schottky barrier sample 4 is carried out voltage scanning and measures the electric current under corresponding bias voltage.
One second lens 6, are placed on the front perpendicular to the Schottky barrier area surfaces direction of Schottky barrier sample 4, converge the light fluorescence sending in Schottky barrier region, incide in the entrance slit of monochromator 7 thereafter.
One monochromator 7, receives the light fluorescence that send in the Schottky barrier region of Schottky barrier sample 4, and light fluorescence is carried out to the selected or scanning of wavelength, incides 8 li of detectors thereafter.
One detector 8 is measured the light intensity of the light fluorescence sending under the different bias voltages in Schottky barrier region of Schottky barrier sample 4 under the selected wavelength of monochromator;
The signal input part of one lock-in amplifier 9 is connected with the signal output part of detector 8, measures the signal of detector 8 output terminals.
One second source table 10 is connected with the output terminal of lock-in amplifier 9, measures the output end voltage of lock-in amplifier 9.
One computing machine 11 is controlled monochromator 7, the first source table 5 and the second source table 10, realize the bias voltage scanning of the first source table 5 to Schottky barrier sample 4, receive the photocathode data under the selected wavelength of monochromator 7 sending in Schottky barrier region under different bias voltages, carry out corresponding signal data processing.Photocathode and bias voltage (dividing potential drop in deduction resistance in series, the lower same) change curve under wavelength selected in the Schottky barrier region that obtains Schottky barrier sample 4.Be less than in schottky barrier height value (unit: eV) scope when forward bias voltage is in, photocathode increases along with the increase of forward bias; Be equal to or greater than within the scope of schottky barrier height value when forward bias voltage is in, photocathode changes not obvious along with forward voltage increase, and intensity is more stable; Therefore, in the change curve of the Schottky barrier area light fluorescence intensity obtaining and bias voltage, when strong 0 degree of light fluorescence starts to stablize with forward voltage increase under forward bias voltage, corresponding bias voltage (unit: V) is exactly the schottky barrier height (unit: eV) of Schottky barrier sample 4.
Light source wherein 1 is for the light source in helium cadmium laser or xenon lamp, tungsten lamp, deuterium lamp is through the selected light of wavelength (photon energy is greater than the energy gap of Schottky barrier sample to be measured) of monochromator or the one of other LASER Light Source (photon energy is greater than the energy gap of Schottky barrier sample to be measured).
The light that first lens 3 wherein sends light source 1 converges to the Schottky barrier region of Schottky barrier sample 4, and the spot size while inciding schottky area is less than Schottky barrier area surfaces.
The first source table 5 wherein offers the plus or minus bias voltage of Schottky barrier sample 4 to be measured, and Schottky barrier sample 4 is carried out voltage scanning and measures the electric current under corresponding bias voltage.
The second lens 6 that converge light fluorescence wherein converge the light fluorescence emitting from Schottky barrier sample 4, incide in the entrance slit of monochromator 7 thereafter.
Detector 8 is wherein photodiode or photomultiplier, measures the strength characteristics of light fluorescence.
Embodiment:
Measuring involuntary Doped GaN, the barrier height of gently mixing silicon GaN Schottky barrier photodetector sample illustrates the present invention as example.
First the barrier height of measuring involuntary Doped GaN Schottky barrier photodetector sample, its concrete steps are as follows:
Step 1: light source 1 uses 325nm He-Cd laser instrument, laser beam is after chopper 2 copped waves, focus on the Schottky barrier region of involuntary Doped GaN Schottky barrier photodetector sample by focusing on first lens 3, the spot size while inciding schottky area is less than Schottky barrier area surfaces.The synchronization output signal of optical chopper 2 is received the reference signal input end of lock-in amplifier 9.
Step 2: adjust involuntary Doped GaN Schottky barrier photodetector sample and sample stage, Schottky barrier area surfaces and incident beam are angled, does not enter the light beam of Schottky barrier area surfaces reflection and converges the second lens 6 and spectrometer 7.
Step 3: one first source table 5 uses source table 2400 to be connected with GaN Schottky barrier photodetector sample, offers the plus or minus bias voltage of Schottky barrier photodetector sample, and Schottky barrier photodetector sample is carried out to voltage scanning.
Step 4: one second lens 6, be placed on the front perpendicular to the Schottky barrier area surfaces direction of GaN Schottky barrier photodetector sample, converge the light fluorescence sending in Schottky barrier region, incide in the entrance slit of monochromator 7 thereafter.
Step 5: a monochromator 7, receive the light fluorescence that send in the Schottky barrier region of GaN Schottky barrier photodetector sample, light fluorescence is carried out to the selected or scanning of wavelength, incide 8 li of detectors thereafter.The wavelength 363.2nm that approaches GaN energy gap as selected in monochromator.
Step 6 a: detector 8 uses photomultiplier, measures the light intensity of the light fluorescence sending under the different bias voltages in Schottky barrier region of GaN Schottky barrier photodetector sample under the selected wavelength 363.2nm of monochromator;
Step 7: the signal input part of lock-in amplifier 9 is connected with the signal output part of detector 8, the signal of measurement detector 8 output terminals.
Step 8: one second source table 10 uses source table 2400, is connected with the output terminal of lock-in amplifier 9, measures the output end voltage of lock-in amplifier 9.
Step 9 a: computing machine 11 is controlled monochromator 7, the first source table 5 (source table 2400) and the second source table 10 (source table 2400), realize the bias voltage scanning of the first source table 5 to involuntary Doped GaN Schottky barrier photodetector sample, computing machine receives the photocathode data of (under the selected output wavelength 363.2nm of monochromator 7) that send under different bias voltages in Schottky barrier region, carries out corresponding signal data processing.Obtain photocathode under the selected wavelength in Schottky barrier region of involuntary Doped GaN Schottky barrier photodetector sample and bias voltage change curve Qundoped as shown in Figure 2.Curve Qundoped from Fig. 2 can find out: be less than within the scope of 1.22V when forward bias voltage is in, photocathode increases along with the increase of forward bias; When forward bias voltage is being equal to or greater than within the scope of 1.22V, photocathode changes not obvious along with forward voltage increase, and intensity is more stable; Therefore, in the Schottky barrier area light fluorescence intensity obtaining and bias voltage change curve Qundoped, when photocathode starts to stablize with forward voltage increase under forward bias voltage, corresponding bias voltage numerical value 1.22 (unit: V) is exactly the schottky barrier height numerical value (unit: eV) of involuntary Doped GaN Schottky barrier photodetector sample, and its schottky barrier height is 1.22eV.
Test sample is changed into and gently mixes silicon GaN Schottky barrier photodetector sample and repeat above-mentioned measuring process, obtain gently mixing the Schottky barrier area light fluorescence intensity (under selected wavelength 363.2nm) of silicon GaN Schottky barrier photodetector sample and the change curve Qdoped of bias voltage as shown in Figure 2, its schottky barrier height is 0.86eV.
For verify the present invention to measuring involuntary Doped GaN, gently mix the validity of silicon GaN Schottky barrier photodetector sample barrier height, we have measured current-voltage (I-V) family curve of two samples, as shown in Figure 3.I-V characteristic formula according to Schottky barrier sample:
In formula, V is bias voltage, I
stit is saturation current.In the time of V >=3kT/q:
By I-V family curve try to achieve involuntary Doped GaN, the saturation current of gently mixing silicon GaN Schottky barrier photodetector sample is respectively: Istundoped=3.08 × 10
-16ampere, Istdoped=5.15 × 10
-11ampere.According to Schottky barrier saturation current formula:
A in formula
*jason Richardson's constant, A
*=26A/cm
2× K
2; A
sthe area of GaN Schottky barrier photodetector sample, A
s=0.0124cm
2; K=300K; The barrier height of obtain involuntary Doped GaN, gently mixing silicon GaN Schottky barrier photodetector sample is respectively: 1.20eV, 0.88eV.
Utilizing the involuntary Doped GaN that apparatus and method of the present invention record, the barrier height of gently mixing silicon GaN Schottky barrier photodetector sample is respectively 1.22eV, 0.86eV, and basic and I-V characteristic is measured respectively the barrier height of respective sample: 1.20eV, 0.88eV are basically identical.
Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of making, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (12)
1. a device of measuring schottky barrier height, is characterized in that, comprising:
One light source, for the optical signal source of this device is provided, to excite the Schottky barrier region of testing sample, sends light fluorescence;
One optical chopper, for the light beam copped wave in the Schottky barrier region to inciding testing sample, synchronization output signal is received the reference signal input end of lock-in amplifier;
One first lens, is positioned at before testing sample, converges light beam that optical signal source sends in the Schottky barrier region of testing sample;
One testing sample, is placed on sample stage, and Schottky barrier area surfaces and the incident beam of this testing sample are angled, the light beam of Schottky barrier area surfaces reflection is not entered and converge the second lens and spectrometer;
One first source table, is connected with testing sample, for plus or minus bias voltage is provided to testing sample, testing sample is carried out voltage scanning and measures the electric current under corresponding bias voltage;
One second lens, are placed on the front perpendicular to the Schottky barrier area surfaces direction of testing sample, converge the light fluorescence sending in Schottky barrier region, incide monochromator thereafter;
One monochromator, for receiving the light fluorescence sending in Schottky barrier region, carries out wavelength to light fluorescence and selectes or scan, and incides detector thereafter;
One detector, for measuring the light intensity of the light fluorescence sending under the different bias voltages in Schottky barrier region under the selected wavelength of monochromator;
One lock-in amplifier, the signal input part of lock-in amplifier is connected with the signal output part of detector, for measuring the signal of detector output terminal;
One second source table, is connected with the output terminal of lock-in amplifier, for measuring the output end voltage of lock-in amplifier; And
One computing machine, be used for controlling monochromator, the first source table and the second source table, realize the bias voltage scanning of the first source table to Schottky barrier sample, in the photocathode from the selected wavelength in Schottky barrier region obtaining and bias voltage change curve, determine schottky barrier height numerical value.
2. the device of measurement schottky barrier height according to claim 1, it is characterized in that, described computing machine receives the photocathode data under the selected wavelength of the monochromator sending under different bias voltages in Schottky barrier region, carry out corresponding signal data processing, obtain photocathode and bias voltage change curve under the selected wavelength in Schottky barrier region; Be less than within the scope of schottky barrier height value when forward bias voltage is in, photocathode increases along with the increase of forward bias; Be equal to or greater than within the scope of schottky barrier height value when forward bias voltage is in, photocathode changes not obvious along with forward voltage increase, and intensity is more stable; Therefore, in the Schottky barrier area light fluorescence intensity obtaining and bias voltage change curve, when photocathode starts to stablize with forward voltage increase under forward bias voltage, corresponding bias voltage numerical value is exactly schottky barrier height numerical value, wherein the unit of bias voltage numerical value is V, and the unit of schottky barrier height numerical value is eV.
3. the device of measurement schottky barrier height according to claim 2, is characterized in that, described computer control monochromator carries out length scanning or selected a certain outgoing wavelength to light fluorescence; Computer control the first source table and the second source table, the first source table is implemented the bias voltage scanning to Schottky barrier sample and is measured the electric current under corresponding bias voltage, the second source table receives the glimmering light intensity of light under corresponding bias voltage, computing machine carries out corresponding signal processing, obtains Schottky barrier area light fluorescence intensity and biasing bias variations curve.
4. the device of measurement schottky barrier height according to claim 1, it is characterized in that, described light source is helium cadmium laser, or be a kind of light source in xenon lamp, tungsten lamp and deuterium lamp light through the selected wavelength of monochromator, be wherein greater than the energy gap of testing sample through the photon energy of the light of the selected wavelength of monochromator.
5. the device of measurement schottky barrier height according to claim 1, it is characterized in that, the light that described first lens sends light source converges to the Schottky barrier region of testing sample, and the spot size while inciding schottky area is less than Schottky barrier area surfaces.
6. the device of measurement schottky barrier height according to claim 1, it is characterized in that, described testing sample surface forms an angle with unpolarized light beam, the folded light beam on incident light and testing sample surface has angle, folded light beam can not be incided and converge in second lens and monochromator of light fluorescence.
7. the device of measurement schottky barrier height according to claim 1, it is characterized in that, described testing sample is the Schottky barrier sample that direct band-gap semicondictor material is made, and photon energy is greater than its Schottky barrier region of light beam irradiates of its energy gap can send light fluorescence.
8. the device of measurement schottky barrier height according to claim 1, is characterized in that, described the first source table provides plus or minus bias voltage to testing sample, and testing sample is carried out to voltage scanning.
9. the device of measurement schottky barrier height according to claim 1, is characterized in that, described in converge light fluorescence the second lens the light fluorescence emitting from testing sample is converged, incide the entrance slit of monochromator thereafter.
10. the device of measurement schottky barrier height according to claim 1, is characterized in that, described monochromator receives the light fluorescence that send in Schottky barrier region, and light fluorescence is carried out to length scanning or selected a certain wavelength, incides detector thereafter.
The device of 11. measurement schottky barrier heights according to claim 1, is characterized in that, described detector is photodiode or photomultiplier, for measuring the strength characteristics of light fluorescence.
12. 1 kinds of application rights require the method for measurement device schottky barrier height described in 1, it is characterized in that, comprising:
Step 1: the laser beam that light source sends, after chopper copped wave, is focused on by first lens on the Schottky barrier region of testing sample, and the spot size while inciding schottky area is less than Schottky barrier area surfaces; The synchronization output signal of optical chopper is received the reference signal input end of lock-in amplifier;
Step 2: adjust testing sample and sample stage, Schottky barrier area surfaces and incident beam are angled, does not enter light beam that Schottky barrier area surfaces reflects and converges the second lens and spectrometer;
Step 3: the first source table is connected with testing sample, provides plus or minus bias voltage to testing sample, carries out voltage scanning and measures the electric current under corresponding bias voltage testing sample;
Step 4: the second lens are placed on the front perpendicular to the Schottky barrier area surfaces direction of testing sample, converge the light fluorescence sending in Schottky barrier region, incide the entrance slit of monochromator thereafter;
Step 5: the light fluorescence that send in the Schottky barrier region of monochromator reception testing sample, light fluorescence is carried out to wavelength and select or scan, incide detector thereafter;
Step 6: the light intensity of the light fluorescence sending under the different bias voltages in Schottky barrier region of detector measurement sample under the selected wavelength of monochromator;
Step 7: the signal input part of lock-in amplifier is connected with the signal output part of detector, the signal of measurement detector output terminal;
Step 8: the second source table is connected with the output terminal of lock-in amplifier, measures the output end voltage of lock-in amplifier;
Step 9: computer control monochromator, the first source table and the second source table, realize the bias voltage scanning of the first source table to sample, computing machine receives the photocathode data that send under different bias voltages in Schottky barrier region, carry out corresponding signal data processing, photocathode and the bias voltage change curve under wavelength selected in the Schottky barrier region that obtains testing sample, obtained the schottky barrier height numerical value of testing sample by this curve.
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| CN103576070B (en) * | 2013-11-18 | 2016-02-17 | 上海电力学院 | A kind of method being extracted schottky barrier height by Photovoltaic measurement |
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