Wide band gap electronic devices

The feature sizes of silicon devices approach values where fundamental physics limitations lead to diminishing returns on investment in further scaling, and wide band gap semiconductor materials look increasingly attractive for many applications, where high electron mobility, high current carrying capabilities, a high thermal conductivity, high temperature operation, and a high breakdown field make them superior to silicon and III-V semiconductor technology. GaN-based devices have demonstrated high-temperature operation with little or no degradation up to 300°C. The most spectacular results have been obtained for AlGaN/GaN microwave power High Electron Mobility Transistors (HEMTs) that yielded over to 11 W/mm power at 10 GHz. The maximum density of the two-dimensional electron gas at the GaN/AlGaN heterointerface or in GaN/AlGaN quantum well structures can exceed 2×10¹³ cm^-2, which is an order of magnitude higher than for traditional GaAs/AlGaAs heterostructures. Very large piezoelectric constants of AlN and GaN can be used in piezoelectric and pyroelectric sensors and could be taken advantage for enhancing the sheet carrier concentration and reducing leakage current in conventional electronic devices. Recently proposed Strain Energy Band Engineering and Pulsed Atomic Epitaxy techniques should allow us to independently control strain and lattice mismatch by using AlInGaN/GaN heterostructures and should find important applications in power devices. SiO₂/AlGaInN/GaN Metal Oxide Semiconductor Heterostructure Field Effect Transistors (MOSHFETs) and SiN/AlGaInN/GaN Metal Insulator Semiconductor Heterostructure Field Effect Transistors (MISHFETs) have exhibited performance superior to that of conventional AlGaN/GaN devices and hold promise for power applications. GaN epitaxial layers can be grown on SiC, which allows us to combine superior transport properties of GaN with a high thermal conductivity of SiC. All this gives hope that electronic devices based on GaN will reach the same prominence as GaN-based blue and white, and UV light emitters.