SU794566A1 - Surface recombination rate measuring method - Google Patents

Description

the magnitude of the electric field strength of one polarity in a constant magnetic field. In addition, it includes measuring the amplitude value of the photoluminescence signal in the absence of electric and magnetic fields and calculating the surface recombination rate of nonequilibrium charge carriers on the illuminated surface of the sample using formula 3.

The disadvantage of this method is that it also does not allow measuring the surface recombination rate on opposite surfaces of the sample in a single measurement cycle, and for performing these measurements it is necessary to perform the above operations twice (for one and the other surface).

The aim of the invention is to simplify the measurement method and make it possible to measure a parameter on both surfaces of the sample in a single cycle.

The goal is achieved in that according to the method, which includes making ohmic contacts to a sample, placing the sample in a magnetic field, creating an electric field strength in it, the vector product of the electric and magnetic fields being perpendicular to the sample surface, focusing the recombination radiation and excitation light with energy exceeding the width of the forbidden band, measuring the dependence of the photoluminescence signal from the illuminated surface and on the magnitude of the electric field strength of one polarity in a constant magnetic field, the polarity of the electric field is additionally alternated, the indicated dependence is measured simultaneously with the unlit surface of the sample, the electric field strengths corresponding to the maximum values of the luminescence signals are recorded, and parameter by the formula:

s.y

Tmax / (")

e G - dimensionless generation of nonequilibrium carrier pairs; 7max - a dimensionless field corresponding to the maximum values of the photoluminescence signals;

P - quantum yield; F (a) is a function depending on y; S- is the dimensionless rate of surface recombination on the illuminated surface; S + is the dimensionless rate of surface recombination on an unlighted surface.

These values are related to the following ratios:

F (a) J (a)

| 1/2 Y

) ./ (a) PJ

g

(-ITTTV

oo

 Eg /rf(2.gr- kT I cn№ r t „+ pp1

9V;, d

E.HTmax -

2ckT

G -,

D-N

20 where g- is the size of the generation rate

nonequilibrium pairs; t „, Sch - effective mass of electrons and

holes, respectively; / I is Planck's constant; 25s - the speed of light;

k is the Boltzmann coefficient; Y is a dimensionless field; - electron mobility; D is the bipolar diffusion coefficient;

n is the refractive index of the material; Eg - the width of the forbidden zone;

G-temperature; 35E - electric intensity

floor;

L is the concentration of uncompensated impurities;

5-dimensional rate of surface recombination;

I am the intensity of the magnetic field; q is the electron charge; L is the diffusion length; d is the sample thickness.

45 The drawing shows a diagram of the implementation of the proposed method. The scheme contains the sample under study 1, equipped with ohmic contacts and leads, electromagnet pole 2, excitation light source 3, focusing lenses 4 and 5, photoluminescence signal receiver 6.

The sequence of operations in the implementation of this method is as follows.

The test sample 1, equipped with 55 ohmic contacts and leads, by means of which an electric field is created in it, is placed between the poles 2 of the electromagnet, and the direction of the vector product of the electric and 60 magnetic fields perpendicular to the surface of the sample 1. The exciting light from the source 3 hits the sample surface through the focusing lens 4. Radiation from surfaces (illuminated and non-illuminated) is focused by lenses 5 and

recorded by receivers 6 photoluminescence signals.

In a semiconductor wafer placed in a crossed electric and magnetic field, under the action of exciting light, nonequilibrium electron-hole pairs are produced, which are affected by the Lorentz force. Depending on the direction of the Lorentz force, which in this method changes due to the application of an alternating polar electric field, the flow of non-equilibrium carriers slows down or accelerates into the sample from the surface. As a result, in the case when nonequilibrium electron-hole pairs accumulate near the illuminated surface, the self-absorption of recombination radiation decreases, and therefore the intensity of the photoluminescence signal from the illuminated surface of the sample increases with increasing electric field strength. At a certain intensity of the electric field, the maximum of the photoluminescence signal is observed. When the polarity of the electric field changes, the concentration of non-equilibrium pairs occurs near the unlighted surface of the sample and a similar dependence of the photoluminescence signal from the unlighted surface of the sample is observed. From the indicated dependences of the photoluminescence signals on the intensity of the electric field, the rate of surface recombination on the illuminated and unlit surfaces of the sample is determined.

By measuring the dependence of the photoluminescence signal on the strength of the electric field simultaneously with the illuminated and unlit surfaces of the sample, which is achieved by alternating the polarity of the electric field and using two receivers of photoluminescence signals, the measurement method is simplified and it becomes possible to measure the parameter of interest on both surfaces of the sample a single cycle when the need to turn the sample is eliminated.

Claims (3)

1. Petrusevich V. А. Physics of a solid body. 1961, T. 3, no. 6, s. 1268. 2.Peka G. P. et al. Determination of the recombination parameters of semiconductors from photoluminescence excitation spectra. 1975, v. 9, no. 10, s. 1920-1924. 3. Patent of the GDR No. 84687, cl. 21e 31/26, 1971 (prototype).