Structural and optical properties of Cr-doped semi-insulating GaN epilayers

Mei, F.; Wu, K. M.; Pan, Y.; Han, T.; Liu, C.; Gerlach, J. W.; Rauschenbach, B.
September 2008
Applied Physics Letters;9/15/2008, Vol. 93 Issue 11, p113507
Academic Journal
The properties of Cr-doped GaN epilayers grown by rf-plasma-assisted molecular beam epitaxy were studied. The deep acceptor nature of Cr was used to grow semi-insulating GaN epilayers on sapphire substrates for electronic device applications. The room-temperature (RT) sheet resistivity of the epilayers reached 1010 Ω/square. The activation energy of dark conductivity was about 0.48 eV. Step-graded AlxGa1-xN/GaN (x=0.3-0.2) superlattices (SLs) were designed to filter dislocations. Transmission electron microscopy images showed that the SLs can dramatically reduce dislocation density. Al0.35Ga0.65N/GaN heterostructure grown on Cr-doped semi-insulating GaN epilayer exhibited a RT mobility of 960 cm2/V s and sheet carrier density of 2.1×1013 cm-2.


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