CN103576070A - Method for extracting height of Schottky barrier through photovoltaic value measurement - Google Patents
Method for extracting height of Schottky barrier through photovoltaic value measurement Download PDFInfo
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- CN103576070A CN103576070A CN201310577467.8A CN201310577467A CN103576070A CN 103576070 A CN103576070 A CN 103576070A CN 201310577467 A CN201310577467 A CN 201310577467A CN 103576070 A CN103576070 A CN 103576070A
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Abstract
The invention relates to a method for extracting the height of a Schottky barrier through photovoltaic value measurement. In the method, the height of the Schottky barrier is extracted by measuring the photovoltaic value of a pn junction photovoltaic photodiode. The method specifically comprises the following steps that firstly, under the open-circuit condition, a background light source shines on the pn junction photovoltaic photodiode, the steady-state photovoltaic value of the photodiode is measured, and the illumination intensity of the background light source is increased continuously until the steady-state photovoltaic value of the photodiode is not increased any more; secondly, when the steady-state photovoltaic value of the photodiode is not increased any more, ultrafast pulse lasers shine on the photodiode, the illumination intensity of incidence lasers is increased continuously to saturate the measured transient-state photovoltaic value of the photodiode, and the minimal value V1 of the transient-state photovoltaic value is acquired; thirdly, calculation is carried out through formulas to acquire the electrode interface Schottky barrier height of the pn junction photovoltaic photodiode. Compared with the prior art, the method has the advantages of being capable of effectively reducing interference, simple, convenient to use, high in sensitivity, free of damaging devices, strong in practicability and the like.
Description
Technical field
The present invention relates to a kind of semiconductor science and technical field, especially relate to a kind of method of extracting schottky barrier height by Photovoltaic measurement.
Background technology
The peculiar ohmic contact characteristic of metal-semiconductor contact interface and Schottky contact properties are the cores of semiconductor devices and large scale integrated circuit.Ohmic contact can be used for the input, output of semiconductor devices signal and each is interelement interconnected, and Schottky contact properties has determined the parameter of device performance, is the foundation of semiconductor device design.For typical pn knot photovoltaic type photodiode, except device self pn junction characteristic, its complementary characteristic is device ghost effect (comprising metal/semiconductor contact and electricresistance effect thereof).In each component of ghost effect, metal/semiconductor contact is under the impact of the factors such as gold, half work function difference and System of Detecting Surface Defects For Material, and the electrode of making is not often ohmic properties, even forms Schottky contacts.Be embodied in larger contact resistance and thicker barrier layer, under simple being similar to, be equivalent to metal and semiconductor material and form a class pn knot, the built in field of its built in field direction and pn knot is contrary, thus form two back-to-back, the asymmetric pn junction structure of character.This contact performance will affect the figure of merit R of detector
0a, noise, I-V characteristic, response speed and responsiveness.Along with photoelectronic imaging device is constantly to greatly the dwindling of the paroxysm of large scale array face exhibition, particularly pn junction depth and contact hole area, the Schottky contacts at metal/semiconductor interface is also more and more large on the impact of photoelectric device.For guaranteeing that device has good performance, the Schottky contacts effect at metal/semiconductor interface is wished the smaller the better.
Metal/semiconductor contact performance and semi-conductive doping content are closely related, although therefore there is the method for several formation Ohmic contact, but most devices is the technology that adopts heavily doped mode that interface potential barrier layer is become as thin as a wafer up to now, make charge carrier carry out current transfer in the mode of tunnelling, thereby formed " accurate Ohmic contact ".Yet in order to control the tunnelling current of pn knot, the region on pn knot both sides can not all adopt heavily doped mode, has become so reduce metal/semiconductor contact berrier the most effectual way that reduces Schottky contacts effect.Low contact berrier will be the only way of realizing ultralow Contact Effect.
But for metal/semiconductor Interfacial Potential Barrier height pn knot photovoltaic type photodiode on the low side, its rectification characteristic will become not obvious and even disappear, thereby often present the illusion of Ohmic contact.This is due to the now impact impact on current characteristics far above Schottky barrier of device self pn junction characteristic.Yet in traditional current-voltage test (I-V), capacitance-voltage measurement (C-V), while only having metal/semiconductor interface Schottky contacts effect comparatively significantly, just can obtain interface information, therefore, method by test I-V, C-V feature extraction interface schottky barrier height often lost efficacy, and this just needs research and establish reliable pn knot photovoltaic type photodiode metal/semiconductor interface schottky barrier height to characterize new method.For this reason, the present invention proposes a kind of method based on photovoltaic Test extraction pn knot photovoltaic type photodiode metal/semiconductor interface schottky barrier height, and has been successfully used to the extraction of mercury cadmium telluride (HgCdTe) pn knot infrared photoelectric detector schottky barrier height.
Summary of the invention
Object of the present invention is exactly to provide a kind of effective minimizing to disturb, by Photovoltaic measurement, extract simply and easily the method for schottky barrier height in order to overcome the defect of above-mentioned prior art existence.
Object of the present invention can be achieved through the following technical solutions:
By Photovoltaic measurement, extract a method for schottky barrier height, the method extracts schottky barrier height by measuring the photovoltaic of pn knot photovoltaic type photodiode, specifically comprises the following steps:
1) under open-circuit condition, with background light source, irradiate pn knot photovoltaic type photodiode, measure the stable state photovoltaic of photodiode, constantly strengthen background light source intensity of illumination until the stable state photovoltaic of photodiode no longer increase;
2) after stable state photovoltaic value no longer increases, adopt ultrafast pulse Ear Mucosa Treated by He Ne Laser Irradiation photodiode, constantly strengthen incident laser light intensity, the photodiode transient state photovoltaic measuring is reached capacity, do not obtain transient state photovoltaic minimal value V
1;
3), by following computing formula, obtain pn knot photovoltaic type photodiode electrode interface schottky barrier height
Wherein,
for pn knot photovoltaic type photodiode electrode interface schottky barrier height under zero-bias, unit is volt; K is Boltzmann constant; The absolute temperature of sample when T is experiment measuring, unit is for opening; Q is electron charge electric weight; N
afor the acceptor density that mix in diode p district, unit is every cubic centimetre; N
dfor the donor density that mix in diode n district, unit is every cubic centimetre; n
iintrinsic carrier concentration during for experiment measuring under sample absolute temperature of living in, unit is every cubic centimetre; V
1for measuring the transient state photovoltaic minimal value of gained, unit is volt; m
*for the effective mass of charge carrier, unit is kilogram; H is Planck's constant.
Described background light source comprises halogen tungsten lamp.
Described ultrafast pulse laser refers to that pulsewidth is that 100 femtosecond to 1 nanoseconds, frequency are the pulse laser of 1 hertz to 1000 hertz.
The present invention extracts schottky barrier height under open-circuit condition, the photovoltaic and the metal/semiconductor interface Built-in potential that due to the knot of pn under open-circuit condition, produce produce the process that photovoltaic does not exist phase mutual interference, therefore by Photovoltaic measurement under open-circuit condition, can farthest embody the information of diode schottky barrier height, improve computational accuracy.Extract schottky barrier height technology and compare with conventional I-V method of testing, C-V method of testing, this method has effectively reduced the become a partner interference of electrode interface schottky barrier height leaching process of pn, particularly solved and can not accurately extract compared with a difficult problem for low Schottky barrier height, thereby can obtain schottky barrier height value accurately, therefore have simple, convenient, highly sensitive, to device not damaged, practical feature.
Accompanying drawing explanation
Fig. 1 is schematic flow sheet of the present invention;
Fig. 2 is photodiode photovoltaic change curve in embodiment.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.The present embodiment be take technical solution of the present invention and is implemented as prerequisite, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.
The photovoltaic effect of the schottky barrier height method of testing based semiconductor device that the present invention proposes.Its theoretical foundation is: the photovoltaic that metal/semiconductor interface Built-in potential produces is photovoltaic extreme value poor of the theoretic maximum photovoltaic of pn junction diode and experiment measuring.According to above-mentioned theory, under open-circuit condition, adopting bias light to irradiate pn knot photovoltaic type photodiode reaches capacity its photovoltaic, adopt on this basis ultrafast pulse Ear Mucosa Treated by He Ne Laser Irradiation diode, its transient state photovoltaic extreme value is reached capacity, utilize Schottky barrier and the relation that measures photovoltaic can calculate the schottky barrier height of this photodiode electrode interface.Concrete derivation is as follows:
1) theoretical according to the photovoltaic effect of pn knot, the photovoltaic of pn knot increases with the increase of intensity of illumination, and its maximum photovoltaic producing equals pn knot Built-in potential V
bi, and the Built-in potential of pn knot can be expressed as:
2) according to metal, contact theory with semiconductor, the schottky barrier height of electrode interface can be expressed as:
V wherein
msbuilt-in potential for metal/semiconductor interface band curvature causes can produce photovoltaic under illumination condition, and maximum photovoltaic equals Built-in potential V
1; E
f-E
vfor the Fermi level of semiconductor material and the electric potential difference of top of valence band, according to semiconductor physics theory, can be expressed as:
3) according to circuit analysis, under open-circuit condition, experiment measuring to photovoltaic should be the poor of the theoretical photovoltaic of pn knot Built-in potential and metal/semiconductor interface Built-in potential generation photovoltaic.
4) according to metal, contact theory with semiconductor, the maximum photovoltaic that metal/semiconductor interface contact electricity produces equals contact electricity.For obtaining the extreme value of metal/semiconductor interface Built-in potential photovoltaic, under open-circuit condition, adopt bias light to irradiate the upper ultrafast pulse Ear Mucosa Treated by He Ne Laser Irradiation diode that adopts in basis, constantly intensifier pulse laser light forces transient state photovoltaic extreme value to reach capacity.The ultrafast pulse laser adopting is that pulsewidth is that 100 femtosecond to 1 nanoseconds, frequency are the pulse laser of 1 hertz to 1000 hertz.Ultrafast pulse laser possesses unique ultrashort pulse, superpower characteristic, can obtain with lower pulse energy high peak light intensity.
5) according to above-mentioned 1), 2) and 3), under open-circuit condition, adopt bias light to irradiate photodiode and make its photovoltaic value of reaching capacity, adopt on this basis ultrafast pulse Ear Mucosa Treated by He Ne Laser Irradiation diode, make its transient state photovoltaic extreme value value of reaching capacity, can derive Schottky barrier and the relation that measures photovoltaic:
Wherein,
for pn knot photovoltaic type photodiode electrode interface schottky barrier height under zero-bias, unit is volt; K is Boltzmann constant, gets 1.38 * 10
-23joule/open; The absolute temperature of sample when T is experiment measuring, unit is for opening; Q is electron charge electric weight, gets 1.6 * 10
-19coulomb; N
afor the acceptor density that mix in diode p district, unit is every cubic centimetre; N
dfor the donor density that mix in diode n district, unit is every cubic centimetre; n
iintrinsic carrier concentration during for experiment measuring under sample absolute temperature of living in, unit is every cubic centimetre; V
1for measuring the transient state photovoltaic minimal value of gained, unit is volt; m
*for the effective mass of charge carrier, unit is kilogram; H is Planck's constant, gets 6.625 * 10
-34joule second.
Adopt halogen tungsten lamp (tungsten halogen lamp, Oriel63355) as standard sources, irradiate the photodiode under open-circuit condition, adopt digital storage oscilloscope (Agilent Infiniium54832B oscilloscope) to gather the photovoltaic signal at diode two ends.Light intensity by continuous enhancing halogen tungsten lamp no longer increases diode photovoltaic.Adopting pulsewidth is 30 psecs, frequency is that the pulsed laser (EKSPLA PG401/DFG) of 10 hertz irradiates diode, constantly intensifier pulse laser light forces the transient state photovoltaic peak of diode to reach minimum value, and the extreme value of measuring diode transient state photovoltaic is extracted schottky barrier height.
As shown in Figure 1, with (T=77K) Hg under liquid nitrogen temperature
0.702cd
0.298the pn knot photovoltaic type infrared photodiode electrode interface barrier height of Te material is extracted as example, and method of testing of the present invention is described:
1) the HgCdTe film pn knot photovoltaic detector that measured photodiode is molecular beam epitaxial growth.P-type Hg
0.702cd
0.298te is grown in take on the CdTe cushion that GaAs is substrate, and the doping content of p-type material is N
a=8 * 10
15cm
-3.At p-type surface Implanted n-Type impurity, doping content is N
d=1 * 10
17cm
-3, form sudden change n
+-on-p knot, junction area is 50 μ m * 50 μ m.Incident light be take substrate in side to light incides pn knot.Photovoltaic signal is through p electrode and the output of n electrode of detector.Test component is placed on and in Dewar container for liquefied nitrogen, carries out coolingly, makes its working temperature approach 77K.At this Cd component and measurement temperature, Hg
0.702cd
0.298the intrinsic carrier concentration of Te material is: 4.42 * 10
8cm
-3, the effective mass of charge carrier is: 3.916 * 10
-31kg.
2) under open-circuit condition, with halogen tungsten lamp, irradiate photodiode, adopt digital storage oscilloscope to gather the photovoltaic signal at diode two ends.By regulate the electric current of halogen tungsten lamp constantly strengthen background light source intensity of illumination until the stable state photovoltaic of photodiode no longer increase.As shown in Figure 2, when the electric current of halogen tungsten lamp is adjusted to 8 ampere-hours, the stable state photovoltaic at diode two ends reaches capacity, and continues to increase halogen tungsten lamp electric current to increase light intensity, on digital storage oscilloscope, do not observe photovoltaic and increase, the photovoltaic at diode two ends is 0.142V.
3) after stable state photovoltaic value no longer increases, adopt ultrafast pulse Ear Mucosa Treated by He Ne Laser Irradiation photodiode, constantly strengthen incident laser light intensity, make to measure transient state photovoltaic peak and reach capacity.As shown in Figure 2, the photovoltaic minimal value V measuring on digital storage oscilloscope
1=0.135V.
4) measuring gained transient state photovoltaic minimal value, bring formula (4) into, obtain pn knot photovoltaic type photodiode electrode interface schottky barrier height:
and adopt in the method for traditional I-V Test extraction pn knot photovoltaic type infrared photodiode electrode interface barrier height, the rectification characteristic that the Schottky barrier that this height is lower is compared with pn knot will become not obvious and even disappear, so be just difficult to extract from I-V characteristic the information of electrode interface, therefore when evaluate electrode quality, sensitivity and reliability are restricted.
Claims (3)
1. by Photovoltaic measurement, extract a method for schottky barrier height, it is characterized in that, the method extracts schottky barrier height by measuring the photovoltaic of pn knot photovoltaic type photodiode, specifically comprises the following steps:
1) under open-circuit condition, with background light source, irradiate pn knot photovoltaic type photodiode, measure the stable state photovoltaic of photodiode, constantly strengthen background light source intensity of illumination until the stable state photovoltaic of photodiode no longer increase;
2) after stable state photovoltaic value no longer increases, adopt ultrafast pulse Ear Mucosa Treated by He Ne Laser Irradiation photodiode, constantly strengthen incident laser light intensity, the photodiode transient state photovoltaic measuring is reached capacity, obtain transient state photovoltaic minimal value V
1;
3), by following computing formula, obtain pn knot photovoltaic type photodiode electrode interface schottky barrier height
Wherein,
for pn knot photovoltaic type photodiode electrode interface schottky barrier height under zero-bias, unit is volt; K is Boltzmann constant; The absolute temperature of sample when T is experiment measuring, unit is for opening; Q is electron charge electric weight; N
afor the acceptor density that mix in diode p district, unit is every cubic centimetre; N
dfor the donor density that mix in diode n district, unit is every cubic centimetre; n
iintrinsic carrier concentration during for experiment measuring under sample absolute temperature of living in, unit is every cubic centimetre; V
1for measuring the transient state photovoltaic minimal value of gained, unit is volt; m
*for the effective mass of charge carrier, unit is kilogram; H is Planck's constant.
2. a kind of method of extracting schottky barrier height by Photovoltaic measurement according to claim 1, is characterized in that, described background light source comprises halogen tungsten lamp.
3. a kind of method of extracting schottky barrier height by Photovoltaic measurement according to claim 1, is characterized in that, described ultrafast pulse laser refers to that pulsewidth is that 100 femtosecond to 1 nanoseconds, frequency are the pulse laser of 1 hertz to 1000 hertz.
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| JP3685429B2 (en) * | 1996-08-06 | 2005-08-17 | シャープ株式会社 | Schottky junction analysis method, semiconductor wafer evaluation method, insulating film evaluation method, and Schottky junction analysis device |
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