Material and Device Properties of 3” Diameter GaAs-on-Si with Buried P-type Layers

Abstract

Two problems facing MOCVD grown GaAs-on-Si are firstly, scale up to 3” and greater wafer diameter with acceptably uniform layer thicknesses and electrical and optical properties, and secondly the achievement of adequate device isolation through the use of buffer layers of low doping density (≤1014 cm−3). We have investigated the thickness uniformity and 300K photoluminescence intensity of 3” Ø, MOCVD grown GaAs layers on Si substrates by whole wafer mapping of these parameters, and correlate the variations found with the gas flow direction during deposition of the GaAs. We have overcome the high background doping densities (n =5−20 × 1015 cm2) in the material by a buried Be implant (1−5 × 1012 at 120 keV) followed by 850°C, 3 sec annealing. This provides adequate isolation for MESFETS and we fabricated such devices with gm's of 160-175 mS mm−1 using our standard process. These values are similar to homoepitaxial MESFETS fabricated in the same way.