Speaker
Description
Wide-bandgap semiconductors such as gallium nitride (GaN) have inherent advantages based on their material properties such as high critical field, high electron mobility and most importantly, high bond energies that lead to lower displacement damage, all of which imply a high radiation hardness. This material system should therefore be considered as an alternative to silicon-based detectors for next-generation colliders. Here, we report on preliminary results of Schottky devices composed of 8 µm thick GaN epitaxially grown with no intentional doping on n+ GaN substrates using Hydride Vapor Phase Epitaxy (supplied by Kyma) and fabricated at NRC Canada. Capacitance measurements reveal low background carrier concentrations ~1E15 cm-3 and average pixel capacitance of 3 nF/cm2. Dark currents of devices with various areas, including guard rings, provide evidence of bulk dominated leakage currents. After rapid thermal anneal treatment dark currents of ≤ 5 nA/cm2 for reverse bias of -1 V were observed. The barrier height of the Schottky contact was extracted using forward biased conditions at room temperature and estimated to be 0.7-0.75 eV, in reasonable agreement with literature data of Ni/GaN barriers although with some inhomogeneity. Devices were also subjected to reverse biases of 200 V with no breakdown behaviour. Preliminary light injection measurements were performed using a focused laser at 355 nm with a spot size of 10 µm adjacent to a 1 mm diameter device. Although carrier collection was observed, it is too early to quantitatively assess the carrier collection efficiency. Furthermore, no strong dependency on bias was observed. Further processing development is planned using NTT’s GaN epi on GaN substrates grown by MOCVD.
