Planar Reactive Deposition Research Articles

Large grains of InP and CdTe on recrystallized CdS substrates

Thin films (∼1 mm) of large-grained (∼40 mm×∼40 mm) InP were epitaxially deposited on low-cost recrystallized CdS substrates at 280 °C by planar reactive deposition. Large grains of CdTe (∼40 mm) were also deposited on similar substrates at 460 °C by physical vapor deposition. Typically, the recrystallized CdS grain size is about 40 mm. However, grains with dimensions up to 300 mm were observed.

InP-on-CdS thin film heterostructures

Thin films of InP were deposited on single crystals and thin films of CdS by the planar reactive deposition technique. Good local epitaxy was observed on single crystals of CdS as well as InP and GaAs. The electrical evaluation of unintentionally doped films on semi-insulating InP substrates show them to be n-type with room temperature electron concentrations ranging from 5 × 1016 cm−3 to 5 × 1017 cm−3 and mobilities up to 1350 cm2/Vsec. For films intentionally doped with Mn and Be, p-type films were obtained. For Mn doping (deep acceptor level), room temperature mobilities as high as 140 cm2/Vsec and free carrier concentrations as low as 5 × 1016 cm−3 (with dopant level of 3 × 1018 cm−3) were obtained. For Bedoped films, free carrier concentrations of about 5 × 1018 cm−3 and mobilities of 20 cm2/Vsec were found. Scanning electron microscope and microprobe pictures show appreciable interdiffusion between the InP/CdS thin-film pair for InP deposited at 450°C. The loss of Cd from the CdS and the presence of an indium-cadmium-sulfur phase at the InP/CdS interface were observed. Interdiffusion is alleviated for InP deposition at lower temperatures.

InP epitaxial thin-film formation by planar reactive deposition

Complete InP epitaxy on GaAs and twinned InP epitaxy on CdS were achieved below 390 °C by planar reactive deposition (PRD). In this technique, indium metal is evaporated from a planar source with an integral cavity into which PH3 gas is introduced and decomposed. The decomposition reaction products, P2 and H2, are emitted from within the source cavity through a perforated top plate and the combined In, P2, and H2 vapor stream on arrival at the substrate forms InP films. High-energy electron diffraction and SEM measurements show the crystallographic quality of the resultant films to be limited by the substrate quality.