Role of deep levels in semi-insulating gallium arsenide pulse-compression photoconductive switches*

The pulse-compression photoconductive switch (PCPS) is a unique high-frequency optoelectronic device that leverages the transferred electron effect in certain semi-insulating (SI) III-V semiconductors like GaAs to realize applications with bandwidths > 100 GHz.¹ However, defects present in SI GaAs can significantly influence the PCPS' operation. In this work, we theoretically show the impact of deep levels on electrical characteristics of a GaAs PCPS in both dark and illuminated mode. Specifically, we study electron dynamics in an illuminated two-dimensional PCPS structure using a commercial transport solver and apply a trap extraction methodology² to examine the transient response of the device during turn-off. In addition, we implement a custom solver to shed light on the steady-state response of PCPS in dark mode by incorporating avalanche effects. We show that recombination centers are crucial for fast turn-off when optical bias is high. In contrast, electron traps degrade peak output current and available bandwidth of the PCPS. To conclude, it is possible to semi-quantitatively characterize major deep levels and their impact on the PCPS performance without Arrhenius measurements of the device.