STUDIES OF GE-GAAS AND GE-SI HETEROJUNCTIONS.
Abstract
The electrical and photovoltaic characteristics of Ge-GaAs and Ge-Si heterojunctions were investigated. It was found that interface states play an important role in these junctions. Theoretical estimates of the number of interface states indicate that these states have only a secondary effect on the equilibrium band diagram of Ge-GaAs junctions. This was verified by capacitance measurements. On the other hand, interface states completely dominate the band diagram of Ge-Si junctions. Tunneling and recombination currents were found to be the dominant transport mechanism in p-n Ge-GaAs and Ge-Si heterojunctions. The theoretical capacitance of abrupt heterojunctions including the effects of interface states were developed. The results show that interface effects depend on the bulk impurity concentrations and their ratio as well as the density and distribution of interface states. Good agreement was obtained between this theory and experimental results. A frequency dependent capacitance term, which is due to the rate limited charging and discharging of the interface states, was observed on several Ge-Si junctions. Photovoltaic measurements indicate that minority carriers generated in the narrow band gap material recombine at the interface. This effect usually nullifies any advantage obtained from the 'window' effect. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1965
- Accession Number
- AD0623842
Entities
People
- Joseph P. Donnelly
Organizations
- Carnegie Institute of Technology