CN104022163A - Improved radiating GaAs-based terahertz frequency doubling Schottky diode - Google Patents

Abstract

The invention discloses a GaAs-based terahertz frequency multiplier Schottky diode with improved heat dissipation, which relates to the technical field of Schottky diodes in the terahertz frequency band, including a semi-insulating GaAs substrate and a heavily doped GaAs layer on the semi-insulating GaAs substrate 1. A low-doped GaAs layer on a heavily-doped GaAs layer, a silicon dioxide layer, an ohmic contact metal layer and a passivation layer, wherein the passivation layer is all diamond. Diamond with high thermal conductivity is used as the passivation layer of the terahertz Schottky frequency doubling diode, which greatly improves the heat dissipation performance of the Schottky diode and improves the frequency doubling efficiency of the Schottky diode.

Description

A thermally improved GaAs-based terahertz frequency-doubling Schottky diode

technical field

The invention relates to the technical field of Schottky diodes in the terahertz frequency band.

Background technique

In the low-end range of terahertz (THz) frequencies, solid-state sources are usually obtained by frequency doubling of semiconductor devices. This method doubles the frequency of the millimeter wave to the THz frequency band through a nonlinear semiconductor device, and has the advantages of compact structure, easy adjustment, long life, controllable waveform, and normal temperature operation. At present, short-wavelength submillimeter wave and THz solid-state sources are mainly obtained by frequency doubling. The use of Schottky diode devices to achieve high-efficiency frequency multiplication not only has a simple circuit structure and high frequency multiplication efficiency, but also has the advantages of high output power of the oscillation source, high frequency stability of the frequency multiplication amplifier chain, and low phase noise; at the same time, Xiao Tertyl diode devices can work stably in the entire millimeter-wave and sub-millimeter-wave frequency bands from 30GHz to 3000GHz. At present, advanced varactor diodes (produced by research institutions such as RAL and VDI) can already work at 3.1THz, and have good continuous wave power and efficiency. Therefore, Schottky diode high-efficiency frequency multiplication technology is very suitable for high-performance millimeter wave, submillimeter wave, and THz systems, and is a THz frequency source technology with great research and application value. Due to its extremely small junction capacitance and series resistance, and high electron drift speed, planar GaAs Schottky diodes have been widely used in the THz frequency band and are the core solid-state electronic devices in the THz technology field.

For the terahertz frequency band, due to the high frequency band, the fundamental power input to the frequency multiplier is limited. In order to obtain greater output power, it is necessary to improve the frequency multiplication efficiency of the frequency multiplier. Studies have shown that when Schottky diodes are used for frequency doubling, heat dissipation has a great impact on their efficiency. As the temperature rises, the efficiency of the Schottky doubler diode decreases. Therefore, it is very necessary to reduce the operating temperature of the frequency doubling device, that is, the operating temperature of the Schottky diode that plays a core nonlinear role. In the prior art, silicon dioxide is used as a passivation layer, and its heat dissipation effect is poor, resulting in low frequency doubling efficiency of the Schottky diode.

Contents of the invention

The technical problem to be solved by the present invention is to provide a GaAs-based terahertz frequency doubling Schottky diode with improved heat dissipation. Diamond with high thermal conductivity is used as the passivation layer of the frequency doubling diode, which effectively improves the terahertz frequency doubling Schottky diode. The heat dissipation of the base diode improves the frequency doubling efficiency of the terahertz frequency doubling Schottky diode.

In order to solve the above technical problems, the technical solution adopted by the present invention is: a GaAs-based terahertz frequency-multiplier Schottky diode with improved heat dissipation, including a semi-insulating GaAs substrate, a heavily doped GaAs layer on the semi-insulating GaAs substrate 1. A low-doped GaAs layer on a heavily-doped GaAs layer, a silicon dioxide layer, an ohmic contact metal layer and a passivation layer, wherein the passivation layer is all diamond.

In a further technical solution, the thickness of the diamond is 20nm-500nm.

In a further technical solution, the diamond is grown on a semi-insulating GaAs substrate and a silicon dioxide layer at a low temperature.

In a further technical solution, the terahertz frequency doubling Schottky diode further includes a thickened metal layer and a Schottky contact metal layer.

The beneficial effect of adopting the above technical scheme is that the thermal conductivity of diamond is 14 times that of silicon dioxide, and the use of diamond with high thermal conductivity as the passivation layer of the terahertz Schottky frequency doubler diode is different from the use of silicon dioxide as the passivation layer. Compared with the Schottky diode of the layer, when the Schottky diode is used for frequency doubling, the injected fundamental wave power is generally larger, and the junction temperature of the Schottky diode rises. Due to the excellent heat dissipation characteristics of diamond, the Schottky diode will be slowed down. rise in diode junction temperature. Under the same fundamental wave injection power, the Schottky diode with diamond as the passivation layer has a low diode junction temperature and low series resistance of the diode, and the power dissipated by the fundamental wave on the series resistance is reduced, increasing the injection base. The utilization rate of the wave power finally improves the frequency doubling efficiency of the Schottky diode. The frequency doubling efficiency of Schottky diodes using diamond as a passivation layer is predicted to increase by about 10% compared to Schottky diodes using silicon dioxide as a passivation layer.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic cross-sectional view of A-A' direction in Fig. 1;

In the drawings: 1. Diamond, 2. Silicon dioxide layer, 3. Ohmic contact metal layer, 4. Metal thickening layer, 5. Semi-insulating GaAs substrate, 6. Heavily doped GaAs layer, 7. Low doping Doped GaAs layer, 8, Schottky contact metal layer.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figures 1 and 2, a thermally improved GaAs-based terahertz frequency doubling Schottky diode,

It includes a semi-insulating GaAs substrate 5, a heavily doped GaAs layer 6 on the semi-insulating GaAs substrate 5, a low-doped GaAs layer 7 on the heavily doped GaAs layer 6, a silicon dioxide layer 2, and an ohmic contact metal layer 3 and passivation layer 1. The semi-insulating GaAs substrate 5 is located at the bottom of the terahertz frequency doubling Schottky diode to support the entire terahertz frequency doubling Schottky diode. On the semi-insulating GaAs substrate 5, there is an epitaxially grown heavily doped GaAs layer 6, on the heavily doped GaAs layer 6 there is an epitaxially grown lowly doped GaAs layer 7, and there is a Schottky contact on the lowly doped GaAs layer 7 Metal layer 8, Schottky contact metal layer 8 is Ti/Pt/Au from bottom to top. The ohmic contact metal layer 3 is Ni/Au/Ge//Ni/Au from bottom to top, and is fabricated on the heavily doped GaAs layer 6 . The metal thickening layer 4 is composed of Au, is fabricated on the ohmic contact metal layer 3, and is connected with the Schottky contact metal layer 8 through an air bridge. The silicon dioxide layer 2 is above the low-doped GaAs layer 7 ; the passivation layer 1 is diamond, and is on the entire semi-insulating substrate 5 . The thickness of the diamond is 20nm-500nm. The diamond is grown on a semi-insulating GaAs substrate 5 or a silicon dioxide layer 2 at a low temperature; heavily doped with GaAs, the doping concentration is on the order of 10^18cm ^-3 . Low-doped GaAs, the concentration is 1e16 cm ^-3 ~5e17 cm ^-3 .

The terahertz frequency multiplier Schottky diode described in the present invention can be realized through mature Schottky diode processing technology. At present, the manufacturing technology of Schottky diode is mature at home and abroad, including cathode ohmic contact, anode Schottky metal Evaporation, air bridge connection and isolation trench etch, make passivation layer. After the front processing is completed, the back is thinned and sliced to produce a terahertz double frequency Schottky diode.

The present invention mainly introduces diamond as the passivation layer of the terahertz frequency doubling diode. It can be seen from the accompanying drawings that the diamond covers most of the area of the Schottky diode, which can effectively improve the heat dissipation when used as a frequency doubling device and improve its performance. Frequency doubling efficiency.

Considering the reliability of GaAs devices, the diamond used in the present invention must be grown in a low temperature method.

Diamond is known as a new generation of wide-bandgap semiconductors. It is a wide-bandgap material and the material with the highest thermal conductivity known, up to 120W/cm K (-190°C), generally up to 20W/cm · K (20°C), about 14 times that of silicon dioxide. The use of diamond materials in terahertz Schottky frequency doubling diodes can improve the heat dissipation performance of terahertz frequency doubling Schottky diodes and increase their frequency doubling efficiency. the

Claims (4)

1. A heat-dissipating improved GaAs-based terahertz frequency doubling Schottky diode, including a semi-insulating GaAs substrate (5), a heavily doped GaAs layer (6) on a semi-insulating GaAs substrate (5), a heavily doped A low-doped GaAs layer (7), a silicon dioxide layer (2), an ohmic contact metal layer (3) and a passivation layer (1) on the GaAs layer (6), characterized in that the passivation layer (1) All are diamonds. 2. A heat dissipation improved GaAs-based terahertz frequency doubling Schottky diode according to claim 1, characterized in that the thickness of the diamond is 20nm~500nm. 3. A heat dissipation improved GaAs-based terahertz frequency doubling Schottky diode according to claim 1, characterized in that the diamond is on a semi-insulating GaAs substrate (5) and a silicon dioxide layer (2) grown at low temperature. 4. A heat dissipation improved GaAs-based terahertz frequency doubling Schottky diode according to claim 1, characterized in that the terahertz frequency doubling Schottky diode also includes a metal thickening layer (4) and Schottky base contact metal layer (8).