RU2780380C1 - Planar gunn diode - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention can be applied in the national economy, more specifically, in medicine, military industry, etc. The stated positive effect will be obtained if the following conditions are fulfilled simultaneously: the active semiconductor element of the Gunn diode of the UHF generator has a planar structure; the span distance from the cathode contact to the anode contact is in the range of (3 to 4) mcm; the ratio of the conductive cross-sectional area of the cathode contact (S_k) to the corresponding area of the anode contact (S_a) is in the range S_k=(0.9 to 0.95)*S_a; the value of the doping level of the current carriers in the active (working) layer is in the range of (1 to 1.5)*10¹⁵ cm³.

EFFECT: use of the invention allows for a significant increase in the performance coefficient of UHF generators on Gunn diodes, allowing for an expansion of the functional range thereof.

1 cl, 1 dwg

Description

The invention relates to microelectronics, specifically to the design parameters of the active region of the planar structure of the Gunn diode. The amount of doping of current carriers in the working layer is equal _to the value located in the range ~ (1.- _1.5 ) * 10 ¹⁵ cm ^-3 . A microwave generator with a planar structure Gunn diode made of GaAs with the given parameters of the active layer in the range of the first harmonic can have an efficiency of up to ~ 40% and a smoothly varying microwave output power level of up to 10%. The present invention will find wide application in the industrial production of microwave generators used in military equipment, medicine, agriculture, etc.

A well-known design of the Gunn diode, made in [1], and including a semiconductor active element, consisting of two layers of highly alloyed GaAs, coated with a layer of contact metal and are cathode and anode contacts. Between the GaA contact layers, there is an active layer of low-doped GaAs. It is connected with one contact to the heat-removing electrode of the body of the Gunn diode, the other - with a flexible metal conductor, which is connected to another electrode of the body of the Gunn diode. When a constant voltage is applied to the Gunn diode, moving domains of a strong field are formed in it, which determine the generation frequency of the microwave generator. In this mode (transit mode), the frequency of microwave generation is determined by the thickness of the active layer and is equal to ~ 1/T, where T is the time of movement of the strong field domain from the cathode to the anode. The frequency of microwave tuning and the output microwave power of the microwave generator are small and are determined by the thickness of the active layer.

The disadvantage of this design is a small operating microwave range, a low level of output midrange power limited by the flight mode.

In [2], the author states that there is no dependence between the operating microwave frequency and the thickness of the low-doped GaAs active layer, which makes it possible to significantly increase both the frequency tuning range of the microwave generation and the generated output microwave power of the Gunn diode. In this case, we are talking about the so-called "Limited Space Charge Accumulation" mode (ONOS mode). The paper [3] substantiates the requirement for the physical parameters of the GaAs semiconductor material used to manufacture Hann diodes operating in the ONOS mode.

n=(2-20)*10 ⁴ *L, where:

n is the doping level of the active layer (1/cm ³ );

L is the length of the active layer (μm).

Gunn diodes made from GaAs semiconductor material with the above requirements are not produced by the electronics industry.

The paper [4] describes the design of a Gunn diode with a doping profile of current carriers in the active layer. The thickness of the active layer is 80 microns. The doping concentration of current carriers at the boundaries of the active layer is respectively equal to the minimum (1*10 ¹³ cm ^-3 ) and maximum (3*10 ¹³ cm ^-3 ) values and increases linearly along the thickness from the minimum to the maximum values. These parameters of the active layer make it possible, when the supply voltage changes from 26 volts to 37 volts, to change the frequency of microwave generation from 26 GHz to 6 GHz, respectively. This effect of microwave generation tuning is explained by the fact that when the supply voltage changes, the length of the span region changes accordingly, thereby changing the frequency of microwave generation. The conversion of direct current energy into alternating current occurs in the transit region of the active layer. At the maximum supply voltage, the span area is maximum and equal to the thickness of the active layer, which corresponds to the maximum energy conversion. Since the span length is maximum, the frequency of microwave generation will be minimum. In this case, it is equal to 6 GHz. A decrease in the operating voltage leads to a decrease in the length of the transit region in the active layer, and, accordingly, the frequency of the output microwave generation will increase. In this situation, in part of the active layer, the electric field strength becomes less than the threshold electric field for the onset of instability. This part of the active layer will play the role of a series-connected parasitic resistance, on which part of the energy will be dissipated. This will lead to the fact that with an increase in the frequency of microwave generation, there will be a significant decrease in the conversion of the energy of a constant electric field into an alternating one. It is physically obvious that the ratio of the maximum to the minimum values of the generated microwave powers is proportional to the ratio of the thicknesses of the maximum and minimum span regions. And when taking into account the parasitic resistance formed in series, this ratio will be even greater.

In this case, the drop in the generated microwave power in the indicated frequency range is six or more times, which is a significant disadvantage of Gunn diodes with this doping profile.

In [5], a microwave generator is presented, containing active and frequency and power control elements, each made on a field-effect transistor with a Schottky barrier according to a common-source circuit. One end of the oscillatory system is connected to the gate of the field-effect transistor with a Schottky barrier of the active element, and the other end is connected to the drain of the field-effect transistor with a Schottky barrier that controls the frequency of the element. The active element is connected to the appropriate sources through power filters. At the same time, the above structure is made in the form of an integrated circuit on one of the sides of the insulating substrate, and on its other side, a metal film 5-10 μm thick is made, in which a longitudinal axisymmetric slot is made, short-circuited at one end. The conductor of the oscillatory system, connected to the gate of the field-effect transistor with a Schottky barrier of the active element, is located perpendicular to the longitudinal axisymmetric slot. The source and drain of the field-effect transistor with a Schottky barrier, which controls the power of the element, are connected to the metal film through through metallized holes in the insulating substrate on both sides of the longitudinal axisymmetric slot at a distance each equal to a quarter of a wavelength, both from the short-circuited end of the longitudinal axisymmetric slot, and from the mentioned conductor of the oscillatory system.

The disadvantages of the output characteristics of this microwave generator are as follows:

1. small range of microwave tuning;

2. large drop in the generated microwave power;

3. low level of output microwave power.

As a prototype, the design of the Gunn diode, made using the mesa technology [6], is used. The design parameters of the GaAs material used in the manufacture of the Gunn diode are as follows:

1. The value of the thickness of the active layer of the Gunn diode is in the range (1.0-1.8) microns.

2. The values of the doping level of current carriers in the active layer change uniformly from (1.1-1.4)*10 ¹⁶ cm ^-3 , at the first boundary of the active layer, to (1.8-2.4)*10 ¹⁶ cm ^-3 at the second boundary of the active layer.

Microwave generators using Gunn diodes with the above parameters as active elements have a low level of efficiency of the output microwave power, which is their disadvantage.

The purpose of this invention is to increase the efficiency of the generated microwave power (~ up to 40%), while maintaining the range of microwave tuning and the minimum drop generated in this microwave range, microwave power.

The goal is achieved by the simultaneous fulfillment of the following conditions.

1. The active, semiconductor element of the Gunn diode of the microwave generator has a planar design.

2. The span distance from the cathode to the anode contacts is in the range of (3-4) µm.

3. The ratio of the conductive area of the cross section of the cathode contact (S _k ) to the corresponding area of the anode contact (S _a ) is in the range S _k =(0.9-0.95)*S _a .

4. The value of the doping level of current carriers in the active (working) layer is in the range (1-1.5)*10 ¹⁵ cm ³ .

In FIG. 1 shows the results:

- two-dimensional modeling in the frequency range of Gunn diodes to determine the efficiency of planar (a) and mesa (b) structures;

- one-dimensional modeling in the frequency range of Gunn diodes, to determine the efficiency of mesa (c) structures;

- experimental determination in the frequency range of efficiency. Gunn mesa diodes (d) designs.

Note. Comparison of characteristics (c) and (d) of FIG. 1 was carried out in [6].

CONCLUSIONS.

Based on the result of comparing the characteristics (b - two-dimensional and c - one-dimensional modeling in the frequency range to determine the efficiency of Gunn diodes of mesa structures), one can see their good agreement. This indicates their adequacy. Therefore, with a high degree of probability, the calculated characteristic (a) is also adequate.

LITERATURE

[one]. Pat. USA No. 3422289, M.K. H01K 3/26 dated 1962

[2]. Pat. USA No. 3617940, M.K. H01B 7/14, dated 02.11.1971.

[3]. Shur M., "Modern devices based on gallium arsenide", Ed. "MIR", 1991, p. 253.

[four]. Pat. USA No. 5256579, M. Cl. H01L 47/02, dated 10/26/1993

[5]. Pat. RU No. 2357355, IPC, H03V 19/14 (2006.01).

[6]. Pat. SU No. 2456715, M.P.K., H01L 47/02, dated 04/01/2011.

Claims (1)

Gunn's semiconductor element, consisting of a substrate (N _p ), active (N _a ) and contact (N _to ) layers connected in series, metal contacts formed from a metal layer deposited on the surface of the active (N _a ), characterized in that for the purpose increase in efficiency, the latter has the form of a planar structure, and the span distance from the cathode to the anode contacts is in the range of (3-4) μm, and the ratio of the conductive region of the cross section of the cathode contact (S _k ) to the corresponding region of the anode contact (S _a ) is located in the range S _k =(0.9-0.95)*S _a , and the value of the doping level of current carriers in the active (working) layer is in the range (1-1.5)*10 ¹⁵ cm ³ .

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