A Study of Impact Ionization and Breakdown Phenomena in SiGe Devices.
Abstract
The spectral response and impact ionization coefficient ration of Si(1-x)Ge(x) have been determined. Measurements were made on p+-i-n+ diodes grown by solid/gas source molecular beam epitaxy. The diodes are characterized by reverse breakdown voltages of 4-12V and dark currents of 20-170pA/micrometers 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 A/W in all the diodes tested. The ratio alpha/beta varies from 3.3 to 0.3 in the same composition range, with alpha/beta=1 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 5X10(exp 19) cu cm is obtained. SiGe/Si junction diodes made with this doping technique show good doping profiles and rectifying characteristics.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 03, 1997
- Accession Number
- ADA329784
Entities
People
- P. Bhattacharya
Organizations
- University of Michigan