GaN Based Structures for NEA by MBE and Investigation of Nitrogen Species andPrecursors for Optimum Layer Properties

摘要

We have obtained: ohmic contacts with resistivities below 10(exp -7) Ohm sq cm ton type GaN which are stable at 500 deg C, Pt Schottky barriers with nearly a unity ideality factor which appear stable at operation temperatures of about 500 deg C, AlGaN/GaN MODFETs on sapphire substrates with 1.5 micron gate length exhibiting extrinsic transconductances of about 220 mS/mm, drain currents of about 600 mA/mm and breakdown voltages of over 100 V for a 1 micrometer gate-drain separation, Inverted MODFETs on sapphire with extrinsic transconductances of about 80 mS/mm with lesser output negative conductance due to carrier confinement reducing the current path in the buffer layer, AlGaN/GaN MODFETs on SiC with 1.5 micron gate length exhibiting extrinsic transconductances of about 180 mS/mm, drain currents of about 325 mA/mm with the negative output conductance prevalent on sapphire being absent.