Investment Process Of High Frequency InP Gunn Devices

The key fabrications of Gunn devices are one of most important techniques for Terhz development, and Terhz development is reputation as the sign of promotion in the further. It is high attention that the Gunn sources explore on Terhz domain in the famous international institute. The Gunn diodes have been commonly used for reliable solid-state frequency sources, such as imaging, material analysis, wideband wireless communications and chemical or biological sensing, especially in important microwave and millimeter-wave signal sources converting direct current into radio frequency output power. Gunn oscillators meet some requirements including small dimension and low phase noise devices.This paper presents a practical fabrication process for high-power microwave and millimeter-wave devices, including mesa etching,electrode evaporation, anneal and so on. We observed the non-linear current-voltage curve and the negative different resistance region characteristics corresponding to different dimensional Gunn diodes.In general, the achievements of this paper are as follows:A theoretical model n+nn+graded structure have been established. We investigated the current-voltage curve with different structures. The thermal is low with a low current, as the n+n structure Gunn diode has low potential barrier. While it has high power out in theory, as the good ohmic contact will be fabricated in n+n n+n structure Gunn diodes. The epitaxial structure is most important in Gunn diode process, because it determine the performances, including current and threshold voltage, frequency, output power and so on. Therefore, the investigation of the Gunn diode structure is crucial for the devices achievement.Through the measurement of different size cathode Gunn diode, we get the characters of Gunn diode’s current and voltage. We designed two kinds of InP-based Gunn didoes. One has fixed diameter of cathode area, but it has variant spacing between anode and cathode. The other has fixed spacing, but it has changing diameters. The threshold voltage and saturated current exhibit strong dependence on spacing (10-60μm). The threshold voltages are approximately3.5V and saturated currents are round140-645mA. In this work, the diameters of diode and the spacing between anode and cathode are optimized.We optimized the thermal sink by three steps:the InP substrate was pasted on silicon wafer, and then lapped and polished on its back. Finally, a heat sink layer is formed using RF magnetron sputtering, followed by a20μm-Au using electroplating.