GaN-Based Two-Dimensional Electron Devices

Abstract : We discuss the properties of the two dimensional (2D) electron gas at AlGaN/GaN heterointerface. The density of the 2D gas is affected by piezoelectric effects and by doping levels in both AlGaN and GaN layers. The record vatues of the sheet carrier density have been achieved wfth sheet electron densities of the two-dimensional electron gas on the order of 1.5 x 10(exp13)/cm2 and the sheet carrier concentration in the surface heterostructure channel as high as 4 x 10(exp13)/cm2. At high electron concentration, electrons are divided between the 2D and 3D states, and this division affects the electron mobility in the channeL Optical polar scattering, impurity scattering, and piezoelectric scattering limit the mobility. The largest electron mobility was observed in AIGaN/GaN heterostructures grown on SiC. At room temperature, the mobility is over 2,000 cm2/V-s; at cryogenic ten1peratures, the highest n%obdity is over 10,000 cm2/V-s. These values are high enough for the observation of the Quantum Hall Effect. Multichannel 2D electron structures are being developed that will allow us to achieve a much higher current density and much higher power.