SU508760A1 - "A non-contact method for measuring the concentration of charge carriers in semi-conductors on microwave 4 - Google Patents

Description

where I am the intensity of the magnetic field; I am the length of the microwave in free

nipocTipaHCTiBe; Ер- relative dielectric

pran.metal capacity; eo is the dielectric constant of vacuum;

e is the electron charge. This formula is fair when conditions are met:

ojpT- 3; sor / o) 3; (-3,

where sor-plasma frequency;

e H (OC-G-cyclotron frequency;

c is the speed of light;

w n t - effective conductive mass and cyclotron mass; g is the relaxation time of the charge carrier pulse.

In the case when the first and third conditions are fulfilled, and the co / c 2 1, then the relationship of concentration with I "g is found from the equation:

1 +

(t2 co,.

where MC - tshlo-pernna frequency when H N, „

The minimum of the reflection coefficient corresponds to the value of the magnetic field, at which the real part of the Fogt dielectric constant becomes approximately equal to the dielectric constant of free space (Vogtovskoe dielectric resonance, permeability is the dielectric constant in the plane perpendicular to the direction of the magnetic field strength). The lower limit of concentration measurement is limited by the condition of the first (i.e., 3), and the upper limit by the magnitude of the magnetic field and the microwave wavelength.

When using magnetic fields up to 200 ke and UHF-1 Koleban.i with a wavelength from 1 mm to 3 cm, the values of the measured concentrations at 77 ° K in n-type materials lie at 10 germs (for antimonide and arsenide and 5%). PA in the range of 10- - 5-10). In p-tppa materials, the concentration range is 5-5-lOs cm-s.

FIG. 1 is a block diagram of an installation implementing this method; in fig. 2- the dependence of the power P reflected from the sample on the palr geo magnetic field I, e.

The installation consists of generator I, attenuator 2, coupler 3, waveguide 4, sample 5, detector 6 video amplifier 7, oscilloscope 8, amplifier 9, sensor 10, capacitor battery P, Helmholtz coils 12, Dewar 13 with liquid nitrogen, straightener 14 :

The installation works as follows.

Microwave oscillations from the generator 1 through the attenuator 2 and the directional coupler 3 enters; and a measuring waveguide 4 made of stainless steel. To the measuring flange, waveguide 4 is applied

sample 5.

The power reflected from sample 5 is fixed by a crystal detector detector M. 6. The signal from detector 6 after amplification by video amplifier 7 goes to vertical plates

oscilloscope 8. The horizontal plates of the oscilloscope 8 through the amplifier 9 receives a signal proportional to the magnetic field, taken from the sensor 10. As the sensor 10 can be used. Coil

with a diameter of 20 mm, having 30 turns, connected to an integrating RC-chain. A magnetic field of up to 200 kV is obtained by discharging a capacitor battery 11 with a capacity of 2 mF, assembled from twelve capacitors IM-5-150, through Helmholtz coils 12. The capacitor battery is charged from the rectifier 14. The duration of the magnetic field pulse is 3 ms . Gelymtolts's coils 12, sample 5 and measuring

VOL1NOVOD 4 is placed in the dewar 13 with liquid nitrogen.

The locality of concentration measurements by the described method in the range of not wavelengths of 8 mm - 3 cm reaches 2 mm, if the measuring waveguide is replaced with a narrowed coaxial one; and in the wavelength range of 1–4 mm 0.2–0.3 mM, if a narrowed waveguide is used as the measuring gauge.

When using an oscilloscope with a memory T1 tube and a preliminary calibration of the sweep, the value of the measured concentration can be directly read from the screen of the oscilloscope, which allows using the method for rapid measurements

concentration in the plant. The measurement time in this case is "e over 2-3 mil."

Claims (1)

Invention Formula A contactless method for measuring the concentration of charge carriers in semiconductors on a microwave by placing in the magnetic field of the sample under test, which is pressed to the open flange of a waveguide, that, in order to simplify and provide accuracy of measurement, perpendicular to the direction of wave propagation and the vector of electric field intensity, a pulsed magnetic field is applied, its intensity is measured, at which the dielectric constant is equal to one, which corresponds to the minimum of the microwave wave reflection coefficient, and the concentration of charge carriers is determined by the formula: l; / L (er-y) 2EH where is H „- (Magnetic field strength; / - microwave frequency in free space; e ,, relative dielectric constant of the lattice, 80 is the dielectric constant of wicum mind; e is the electron charge.