SHALLOW DONORS IN EPITAXIAL GAN

Photoluminescence (PL) of GaN is commonly dominated by the annihilatio n of excitons bound to a 34.5 meV deep donor appearing at 3.472 eV (fo r strain free GaN at 4 K), With PL we were able to resolve two additio nal donor bound exciton transitions. The excitons have localization en ergies of 3.7 +/- 0.3 and 11.3 +/- 05 meV. respectively. Using Haynes rule the respective donors lie 56.5 and 18.5 meV below the conduction band. The applicability of Haynes rule could nicely be confirmed by IR absorption where the 1s-2p transition of the 34.5 and 58 meV donor ar e observed. The issue of residual donors in GaN will be discussed in t his contest. (C) 1997 Elsevier Science S.A.