UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES ELECTRONIC SCIENCES LAB
The high 5 x 10 to the 18th power per cc electron density in as-grown GaN is shown to be due to native donors. Precipitation at grain boundaries and in the bulk does not influence these donors but limits the electric fields that can be applied. Compensation with Li can lower the carrier density, but at the expense of breakdown field. Crystal growth by CVD using NH3, although yielding single crystals as large as 1 x 2 x 1 cm, inherently leads to these low resistivities. Annealing or crystal growth under equilibrium very high N2 pressures is indicated.