New concepts and preliminary results for SiC bipolar transistors: ZnSiN2 and ZnGeN2 heterojunction emitters

The relatively large lattice mismatch of AlN, GaN and InN translate into difficulties with device growth, thus placing limits on band gap engineering. Search for new semiconductor compounds compatible with III-nitrides and SiC has resulted in identification of a large family of wide band gap II-IV-N₂ semiconductors. Specifically, ZnGeN₂ and ZnSiN₂ have lattice parameters close to GaN and SiC respectively, making them attractive for optimum device design. High crystalline quality epitaxial layers of ZnGe _xSi_1-xN₂ spanning the entire range of compositions from x=0 to 1 have been grown by low pressure MOCVD technique on sapphire and SiC substrates. Experimental results including x-ray characterization of crystal properties and optical transmittance studies have been performed. Device issues including etching rate, ohmic contact formation (minimum ρ_c=5.3×10^-7 Ω-cm²), and breakdown voltage (1.4×10⁶ V/cm) have been investigated. Each of these measurements has shown that this material system is suitable for novel electronic devices when combined with existing materials technology