Minority carrier transport in heavily doped GaAs controls the performance of bipolar devices such as heterojunction bipolar transistors and solar cells. So-called heavy doping effects (that is, the influence of heavy impurity doping on the band structure, carrier scattering, and recombination) are well-known to profoundly influence the behavior of silicon devices. The influence of heavy impurity doping on the optical properties of GaAs has been extensively studied, but experimental work to assess its influence on the electrical properties of devices is virtually nonexistent. The objective of this research is to experimentally characterize the equilibrium np product and the minority carrier mobility versus majority carrier concentration in GaAs. The research will increase our knowledge of the band structure and minority carrier scattering mechanisms in heavily doped GaAs. It will provide data to test existing theoretical models and information that is essential for device design. An understanding of the band structure changes associated with heavy impurity design may also permit new device options which exploit the heterojunctions that occur naturally as a result of heavy impurity doping.
