Uniform growth of InSb on GaAs in a rotating disk reactor by LP-MOVPE

Abstract

Uniform films of InSb on GaAs substrates have been grown in a vertical, high-speed rotating disk reactor by low pressure MOVPE. Highly uniform and specular films were obtained over a 50 mm diameter wafer placed at the center of a 5 inch diameter wafer platter. Characterization of thickness, sheet resistance, mobility, and surface morphology was performed by SEM, sheet resistance mapping, Hall effect measurements, and Nomarski microscopy. Thickness uniformity, measured at 10 points radially across the wafer with a 3 mm edge exclusion, is as low as 1.84% with an average uniformity over several runs of only 2.8%. Results obtained from Hall mobility measurements taken by a 7 point cross-pattern show an average mobility of 41,030 cm 2/V · s with a coefficient of variation of 7.1% at 300 K. The sheet resistance uniformity, as determined by a 55 point, contactless, eddy current technique, shows a coefficient of variation as low as 1.37% with an average uniformity over 22 consecutive growth runs of only 3.1%. The effects of growth temperature and V/III ratio on the surface morphology and electronic properties were also studied, resulting in high quality epitaxial layers. With a growth temperature of 475°C and a V/III ratio of 18, Hall mobilities as high as 45,000 cm 2/V · s at 300 K and 31,500 cm 2/V · s at 77 K were measured on a 2 μm thick InSb layer. The corresponding carrier concentrations were 2.05×10 16 and 4.57×10 15 cm −3.