GAN BASED III-V NITRIDES BY MOLECULAR-BEAM EPITAXY

GaN and its allied compounds, AlGaN and InGaN, exhibit electrical and optical properties that are well suited for applications to green/blue/UV emitters and detectors, and high temperature electronics. While vacuum deposition of III-V nitrides is not new, only recently have noteworthy results become available. This is in part due to the use of electron cyclotron resonance (ECR) and other reactive nitrogen sources and clean molecular beam epitaxy (MBE) systems. Low-temperature deposition capability, controlled and hydrogen-free environment, and in situ diagnostic capabilities afforded by MBE make this approach attractive for producing novel structures for devices and understanding the growth pathways which are distinctly different from the conventional III-V compounds. Cubic and wurtzite phases of GaN have been grown with MBE on GaAs, Si, sapphire and SiC, 3C and 6H, substrates. The p-type Mg-doped films require no post-anneals for activation, albeit with lower mobilities than those of organometallic chemical vapor deposition (OMCVD) films. Band edge luminescence with negligible yellow emission has been obtained. Electron mobilities are as high as about 600 cm(2)/V . s with n-type doping levels in the high 10(16) cm(-3) in wurtzitic films with cubic phase exhibiting higher values.