A Study of Impact Ionization and Breakdown Phenomena in SiGe Devices.
Final rept. 30 Jun 94-29 Jun 97,
MICHIGAN UNIV ANN ARBOR DEPT OF ELECTRICAL ENGINEERING
Pagination or Media Count:
The spectral response and impact ionization coefficient ration of Si1-xGex have been determined. Measurements were made on p-i-n diodes grown by solidgas source molecular beam epitaxy. The diodes are characterized by reverse breakdown voltages of 4-12V and dark currents of 20-170pAmicrometers 2. The long wavelength cut-off of the diodes increases from 1.2 micrometers to 1.6 micrometers as x increases from 0.08 to 1.0 with a maximum responsivity of 0.5 AW in all the diodes tested. The ratio alphabeta varies from 3.3 to 0.3 in the same composition range, with alphabeta1 at x congruent 0.45. These results have important implications in the use of this material system in various photodetection applications. As part of this project we also investigated the problem of high-level n-type doping of Si and SiGe, which is required for high quality diodes. The use of supersonically injected pulses of phosphine to achieve uniform and high levels of n-type doping in Si during gas-source molecular beam epitaxy was demonstrated. Uniform n-type doping up to levels of 5X10exp 19 cu cm is obtained. SiGeSi junction diodes made with this doping technique show good doping profiles and rectifying characteristics.
- Solid State Physics