UNINTENTIONAL DOPANTS INCORPORATED IN GAAS-LAYERS GROWN BY MOLECULAR-BEAM EPITAXY

The electrical properties of unintentionally doped layers of GaAs grown by MBE have been investigated. A relatively shallow acceptor (0. 027 eV) with a room temperature concentration of 2 multiplied by 10**1**4 cm** minus **3 is generally characteristic of undoped material presently grown by MBE. During experimental investigations, undesirable system configurations leading to higher background doping levels were identified. These configurations include BeO/Ta film substrate heaters, fused quartz/Ta film substrate heaters, and hot stainless steel fixtures illuminated by the Ga oven.