Defects can be conveniently categorized into three types: point, Line, and
areal. In GaN, the important point defects are vacancies and interstitials;
the line defects are threading dislocations; and the areal defects are sta
cking faults. We have used electron irradiation to produce point defects, a
nd temperature-dependent Hall-effect (TDH) and deep level transient spectro
scopy (DLTS) measurements to study them The TDH investigation has identifie
d two paint defects, an 0.06-eV donor and a deep acceptor, thought to be th
e N vacancy and interstitial, respectively. The DLTS study has found two po
int-defect electron traps, at 0.06 eV and 0.9 eV, respectively; the 0.06-eV
trap actually has two components, with different capture kinetics. With re
spect to line defects, the DLTS spectrum in as-grown GaN includes an 0.45-e
V electron trap, which has the characteristics of a dislocation and the TDH
measurements show that threading-edge dislocations are acceptor-like in n-
type GaN. Finally, in samples grown by the hydride vapor phase technique, T
DH measurements indicate a strongly n-type region at the GaN/Al2O3 interfac
e, which may be associated with stacking faults. All of the defects discuss
ed above can have an influence on the de and/or ac conductivity of GaN.