High-Power Nano- and Picosecond Optoelectronic Switches Based on High-Voltage Silicon Structures with p–n Junctions. III. Self-Heating Effects

Abstract

The self-heating effects of optoelectronic switches based on vertical high-voltage structures with p–n junctions (Vertical Photoactivated Semiconductor Switches, VPSS) operating in the high-frequency mode are theoretically studied for the first time. It is shown that the strong temperature dependence of the control-radiation absorbance κ(T) is a major factor controlling the maximum switching frequency f_max and the corresponding maximum crystal temperature T_max, as well as the temperature T and current density j distributions over the device area. Two-dimensional analysis of the simplest electrothermal model of a VPSS embedded into a double coaxial forming line shows that an increase in the switching frequency f leads to current displacement to the device periphery where the temperature is minimum. However, the T and j distributions over the device area remain stable at  f < f_max and T < T_max. Certainly,  f_max and T_max depend on the control-radiation pulse energy, pulse switching power, and heat-removal conditions. For the VPSS based on indirect-gap semiconductors (Si, SiC), they vary within 20–120 kHz and 120–160°C which is quite sufficient for practical applications. However, VPSSs based on direct-gap semiconductors (GaAs, InP) are in fact inapplicable to operation in high-frequency modes due to the fact that the dependence κ(T) is too sharp.