Growth and in situ monitoring of GaN using IR interference effects

Previously we have reported the MOVPE growth of GaN and related materials on (0 0 0 1) sapphire in a close-spaced vertical rotating disk reactor (W. Van der Stricht et al., J. Crystal Growth 170 (1997) 344). In this paper we describe the in situ monitoring of this growth process by infra-red (IR) radiation interferometry using a fiber coupled optical pyrometer. During growth the amplitude of the IR radiation, emanating from the susceptor (transmitted through the substrate and growing layer) exhibits oscillations which as Nakamura (Jpn. J. Appl. Phys. 30 (1991) 1620) has shown, can be used for monitoring GaN deposition. The form of these oscillations can give an insight into the progress of the growth, allowing the effects of a number of growth parameters to be tracked in real time. We will also describe a simple computer model which simulates these oscillations and we show how IR radiation interferometry has been used to monitor growth in a close-spaced vertical rotating disk reactor. Specifically we have studied the effects on morphology and growth rate of parameters such as reactor pressure, nucleation layer growth and overlayer growth temperature.