THE NATURE OF DONOR CONDUCTION IN N-GAN

Single crystal GaN thin films resulting from various deposition techni ques are usually dominated by residual donors. To date, the true natur e of this donor conduction is not known. Nitrogen vacancies, residual oxygen, and growth defects are cited as potential causes for the resid ual n-type conduction. In this communication we present the first syst ematic study of near conduction band edge states in n-type GaN samples deposited over basal plane sapphire substrates using low pressure met al organic chemical vapor deposition. Electron spin resonance, low tem perature photoluminescence, and Van der Pauw-Hall measurements were us ed as the basis for our study. We concluded that the residual n-type c onduction in GaN results from a band of delocalized donors.