Gallium nitride (GaN) based power electronics has attracted much attention in recent years due to its advantages over traditional Si-based power devices in terms of energy conversion efficiency, switching speed, operation temperature, and system size. In the fabrication of advanced vertical power devices, such as junction barrier Schottky diodes, superjunction diodes, and normally-off vertical junction field effect transistors (VJFETs), it is important to produce laterally patterned p-n junctions, i.e., alternating n-type and p-type regions arranged in lateral directions. However, the mechanism of selective area doing of GaN is poorly understood. The characterization of the lateral dopant distribution in selectively doped GaN regions is difficult, due to the spatial resolution limitation of secondary ion mass spectroscopy.
In this work, selective area p-type doping of GaN on GaN bulk substrates was achieved by etching and epitaxial regrowth. The optical properties of p-GaN epilayers grown on an unintentionally-doped-GaN mesa structure have been studied using spot mode cathodoluminescence (CL) and monochromatic CL mapping. A strong variation in the luminescence characteristics has been observed, with the sidewall of the mesa structure being different to the flat upper and lower mesa regions. A comparison with luminescence characteristics of p-GaN films grown with different Mg concentrations indicate that the Mg concentration at the sidewall is significantly lower. The lower Mg concentration at sidewall is attributed to inefficient Mg incorporation of semi-polar growth. This work demonstrates that CL spectroscopy can be used as a nondestructive, contact-free method to probe local p-GaN doping concentration with submicron resolution. The determination of Mg distribution in p-GaN on a mesa structure is important for GaN-based power devices.
5:00 PM–7:00 PM Apr 23, 2019 (US - Arizona)
PCC North, 300 Level, Exhibit Hall C-E