Heterovalent II-VI and III-V semiconductor integration: A platform for solar cell and other optoelectronic device applications

Semiconductor electronic and optoelectronic materials and devices have experienced very rapid development for more than half a century. However, there still remains a lack of closely lattice-matched materials and substrates suitable for the monolithic integration of various kinds of semiconductor devices on a single chip. A new material platform: II-VI (MgZnCdHg)(SeTe) and III-V (AlGaIn)(PAsSb) semiconductor materials lattice-matched to GaSb, InAs and InSb substrates, has been proposed to achieve the goal. These materials have direct bandgaps covering a very broad energy spectrum from far IR (~0 eV) to UV (~3.4 eV) and small thermal mismatch. Such a unique material platform offers opportunities to study new physics such topological insulation in heterovalent superlattice and enables new light emitting devices, multi-junction solar cells, multi-color photodetectors, resonant tunneling diodes, and facilitates monolithic integration of various materials without misfit dislocations to ensure the best quality for device applications. This talk will focus on the following topics: · Latest progress in the MBE growth of these heterovalent structures and their potential applications in ultrahigh efficiency multijunction solar cells, midwave IR VCSELs etc. · Mg_xCd_1-xTe/Mg_yCd_1-yTe (x=0 and 0.13, y>0.24) heterostructures on InSb substrates with record low interface recombination velocity (~1 cm/s) and ultra-long lifetime (3.6 μs), and crystalline CdTe solar cells with record high efficiency greater than 20%, and 1.7 eV Mg_0.13Cd_0.77Te solar cell with efficiency of 11% for Si based tandem cell application · Monolithically integrated CdTe/InSb dual color photodetectors · A platform to study interfacial topological insulator states in various heterovalent superlattice like CdTe/InSb, ZnTe/GaSb, and ZnSe/GaAs.