Effect of p-n junction overheating on degradation of silicon high-power pulsed IMPATT diodes

The thermal limits of the two-drift impact avalanche and transit-time (IMPATT) diode operating in the pulsed mode in the 8-mm wavelength region with a microwave power as high as 30–35 W have been estimated. It is shown that p-n junction overheat at an operating pulse length of 300 ns and a supply current amplitude of 11.3–15 A amounts to 270–430°C relative to an ambient medium. The temperature limit of junction overheating, above which IMPATT diodes rapidly degrade, was determined as 350°C. The presented results of X-ray phase analysis and depth profiles of Au-Pt-Ti-Pd-Si ohmic contact components confirm thermal limits of the IMPATT diode operating in the pulsed mode.

     

Microwave Modulators Based on 4H-SiC p-i-n Diodes

Multidiode broadband microwave signal modulators based on 4H-SiC p-i-n diodes were fabricated and fully characterized for the first time. The diodes used for the modulator fabrication exhibited a blocking voltage of 1100 V, a 100-mA differential resistance of 1-3 Omega, a punch-through voltage (100 V) capacitance below 0.5 pF, and a carrier effective lifetime of 15 ns. The three-diode modulators are characterized by a transmission loss of 1-2 dB and isolation of 27-34 dB in the 2-7-GHz frequency range, while their switching speed is as low as 30 ns. Two-diode modulators were specially designed for high-temperature operation. These modulators are characterized by a transmission loss of 1.1-2.6 dB and isolation of 33-44.5 dB in the 2-7-GHz frequency range at temperatures up to 300degC.     

Dual function sensors for concurrent measurement of temperature and magnetic field in cryogenic applications

Dual function sensors (DFSs) for concurrent measurement of temperature and magnetic field in cryogenic applications have been developed and characterized. The DFS consists of a Ge-on-GaAs film resistance thermometer and an InSb-on-GaAs film Hall-effect magnetic field sensor combined in a single package with dimensions: 3.5 mm wide, 2.2 mm thick and 10.1 mm long. The construction and characteristics of two models of the DFSs; which are intended to provide measurements of temperature in the 1.5–400 K and 0.1–400 K ranges, and magnetic fields up to 30 T, are presented.