It is well known that vertical GaN devices could surpass current lateral GaN switch technology due to higher critical electric fields and higher breakdown voltages from its different geometry, and lower impurity concentration from the superior quality of homoepitaxial films. However, the inconsistency of GaN substrate properties, both within wafer and vendor-to-vendor, makes reliable device fabrication difficult. Here we implement long-range spectroscopic studies of GaN substrates and epitaxial wafers using Raman, photoluminescence, and optical profilometry to assess incoming material and correlate to electrical performance of vertical diodes. We have classified incoming wafers into two general types, and determined that inhomogeneities in the wafers can negatively affect the reverse leakage current of PiN diodes.

9.3.2023_Treidel

9.4.2023_Anderson

The super-lattice power amplifier with diamond enhanced superjunctions (SPADES) is a device that incorporates nanocrystalline diamond superjunctions into the super-lattice castellated field effect transistor (SLCFET), to improve breakdown voltage. A diamond superjunction is formed with p-type nanocrystalline diamond to balance mutual depletion between the two-dimensional electron gas superlattices and the doped diamond in order to reduce the peak electric field in the drain access region.  Formation of the diamond superjunction presents several challenges, such as managing diamond conformality, strain, and control over p-type doping.  Optimization of diamond growth led to conformal films, with low stress, and linear dependence hole concentration from p-type doping, suitable for the SPADES device.