Simulation, Design And Fabrication Of GaAs-based Heterostructure Bipolar Transistor

Heterostructure Bipolar Transistor (HBT) is provided with wide energy gap emitter that greatly increased efficiency that carrier injected from emitter junction and made base resistance lower. With its excellent performance of high-speed, large power, low noise, good linearity and single power supply, HBT can be widely used in field of microwave power, high-speed digital circuit and photo-electronics application.Firstly, the principle, the characteristics, designs, typical materials, structures and simulation were described as well as the recent developments of GaAs-based heterojunction bipolar transistors (HBTs). Then, the material growth, device fabrication process and characteristics of AlGaAs/GaAs HBT, InGaP/GaAs HBT and GaAsSb/GaAs HBT were studied.Following are the main works of this dissertation:1. AlGaAs/GaAs HBT is grown by MBE with a compound As source, and we studied the relationship between material and device through fabricating and testing large dimension HBTs' device. The growth condition is optimized. Many HBTs are based on the AlGaAs/GaAs system because of the relatively mature technology of the materials system, and meanwhile Al_xGa_1-xAs is lattice matched to GaAs for all mole fractions x. Abrupt and graded AlGaAs/GaAs HBTs were designed, and the growth conditions were optimized based on the diffusion of Be and the crystal quality of base. The large dimension AlGaAs/GaAs HBT was fabricated and its DC and Frequency characteristics were measured, which showed good uniform and linearity.2. Recently, InGaP/GaAs has been attracting interest as a substitution to AlGaAs/GaAs for GaAs-based HBT because the former structure has a larger valence band offset, a lower interface recombination velocity, a higher wet etching selectivity and less deep donor lever (DX center). InGaP epilayers were grown by MBE with a GaP decomposition source, which was introduced into China in MBE system. All the results demonstrated that InGaP epilayers grown under optimized conditions were high quality. The large dimension InGaP/GaAs HBT was fabricated and its DC and frequency characteristics were measured, which showed good uniform and linearity, its highest cut-off frequency reached 2.5GHz.3. GaAs/GaAsSb metamorphic HBTs (MM HBTs) have great potential applications because they have both the relative low cost of GaAs-based and highfrequency of InP-based HBT. The GaAs/GaAsottSborfa DHBT were designed and grown by MBE based on the results of MM HEMT. The large dimension HBT was fabricated and its DC characteristics were measured and analyzed. MM HBT is a very promising research project.