Deep Centers and Persistent Photoconductivity Studies in Variously Grown GaN Films

• Published in: MRS Internet journal of nitride semiconductor research 2000, Vol.5 (S1), p.929-935
• Main Authors: Polyakov, Alexander Y., Smirnov, Nikolai B., Govorkov, Anatoliy V., Usikov, Alexander S., Shmidt, Natalie M., Pushnyi, Boris V., Tsvetkov, Denis V., Stepanov, Sergey I., Dmitriev, Vladimir A., Mil’vidskii, Mikhail G., Pavlov, Vladimir F.
• Format: Article
• Language: English
• ISSN: 1092-5783; 1092-5783
• DOI: 10.1557/S1092578300005287

Deep levels studies on a set of n-GaN films grown by MOCVD and HVPE reveal the presence of electron traps with levels near E c −0.25 eV, E c −0.55 eV, E c −0.8 eV, E c −1 eV, hole traps with levels near E v +0.9 eV and a band of relatively shallow states in the lower half of the bandgap. The total density of these latter states was estimated to be some 10 16 cm −3 and they were tentatively associated with dislocations in GaN based on their high concentration and band-like character. None of the electron or hole traps could be unambiguously related with strong changes of diffusion lengths of minority carriers in various samples. It is proposed that such changes occur due to different surface recombination velocities. An important role of E c −0.55 eV traps in persistent photoconductivity phenomena in n-GaN has been demonstrated.