Highly linear temperature sensor using GaN-on-SiC heterojunction diode for Harsh environment applications

In this work, high temperature diode sensors for harsh environment applications are fabricated and comprehensively characterized. The design of the sensors is based on gallium nitride (GaN) on silicon carbide (SiC) heterojunction structures. The GaN layer was grown by the molecular beam epitaxy (MBE) on an n-type SiC substrate. P-type doping of the GaN was achieved using the atomic magnesium (Mg) as a dopant. The heterojunction devices were fabricated using a concentric ring geometry with the diameters ranging from 400 μm to 1000 μm. Temperature dependent characteristics (Vf — T) of these heterojunction devices as well as their sensitivity (mV/K) are comprehensively characterized in a temperature range from 300 K to 650 K using reduced temperature steps. High temperature electrical measurements have demonstrated that these heterojunction devices have highly linear temperature dependent characteristics and are potentially usable as reliable temperature sensors up to at least 650K. Dedicated programs were used to extract the electrical parameters of the devices designed to operate as a temperature sensor.