Effect of Si doping on optical and thermal properties of MOVPE GaN thin layers

Photothermal deflection spectroscopy is used to investigate thermal and optical properties of MOVPE grown GaN thin layers deposited on sapphire substrate. The effects of Si doping on absorption spectrum and gap energy are revealed. Also, doping-induced free carrier absorption is extracted from absorption in the sub-gap region. Moreover, the variations of photothermal signal versus modulation frequency are used to determine thermal properties of these films. The measured thermal conductivity is clearly decreased by Si doping, the main reason should be the phonon scattering on point defects.