Enhanced functionality in GaN and SiC devices by using novel processing

Some examples of recent advances in enhancing or adding functionality to GaN and SiC devices through the use of novel processing techniques are discussed. The first example is the use of ion implantation to incorporate transition metals such as Mn, Cr and Co at atomic percent levels in the wide bandgap semiconductors to produce room temperature ferromagnetism. A discussion is given of the phase space within which single-phase material can be obtained and the requirements for demonstrating the presence of a true dilute magnetic semiconductor. The ability to make GaN and SiC ferromagnetic leads to the possibility of magnetic devices with gain, spin fets operating at low voltages and spin polarized light emitters. The second example is the use of novel oxides such as Sc₂O₃ and MgO as gate dielectrics or surface passivants on GaN. True inversion behavior has been demonstrated in gated MOS-GaN diodes with implanted n-regions supplying the minority carriers need for inversion. These oxide layers also effectively mitigate current collapse in AlGaN/GaN HEMTs through their passivation of surface states in the gate-drain region. The third example is the use of laser drilling to make through-wafer via holes in SiC, sapphire and GaN. The ablation rate is sufficiently high that this maskless, serial process appears capable of achieving similar throughput to the more conventional approach of plasma etching of vias. The fourth example is the use of either ungated AlGaN/GaN HEMTs or simple GaN and SiC Schottky diodes as sensors for chemicals, biogens, radiation, combustion gases or strain. The sensitivity of either the channel carrier density or the barrier height to changes in surface condition make these materials systems ideal for compact, robust sensors capable of operating at elevated temperatures.