Sb-Heterostructure Backward Diode for Millimetre-Wave Detection

Abstract

Sb-heterostructure backward diode (HBD) is one of the most promising candidates for millimitre-wave and terahertz direct detection. Sb-HBDs have demonstrated excellent performance in the millimetre-wave range with high sensitivity, high cut-off frequency and low noise characteristics. Although Sb-HBDs are also predicted to be very promising for terahertz frequency applications, little effort has been made, and few have reported on its operation above 100 GHz. From the material point of view, few have reported on how the material quality affects the device performance. This thesis work encompasses modelling, fabrication and characterisation of Sb-HBDs, to explore the potential of Sb-HBDs for terahertz direct detection and to improve the device performance through material growth optimisation. The first part of this thesis deals with modelling of Sb-HBD diode to perceive the underlying physics of the device and to guide the experimental work. This is done by using Synopsys' TCAD Sentaurus software. As the second part of this thesis, MBE growth of Sb-HBDs has been conducted to investigate the effect of various buffer thicknesses and the tunnelling interface (InAs/AlSb) bonding types.Large scale test diodes were fabricated and the I-V characterisation was assessed at both ambient and cryogenic temperatures. Finally, fabrication techniques of sub-micron scale devices were developed.