Responsivity and impact ionization coefficients of Si sub(1-x)Ge sub(x) photodiodes

• Published in: IEEE transactions on electron devices Vol. 43; no. 6; pp. 977 - 981
• Main Authors: Lee, Jinju, Gutierrez-Aitken, Augusto L, Li, S H, Bhattacharya, Pallab K
• Format: Journal Article
• Language: English
• Published: 01.01.1996
• ISSN: 0018-9383

The spectral response and impact ionization coefficient ratio of Si sub(1-x)Ge sub(x) have been determined. Measurements were made on p super(+)-i-n super(+) diodes grown by solid/gas source molecular beam epitaxy. The diodes are characterized by reverse breakdown voltages of 4-12 V and dark currents of 20-170 pA/ mu m super(2). The long wavelength cut-off of the diodes increases from 1.2 mu m to 1.6 mu m 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 identical with 1 at x approximately equal to 0.45. These results have important implications in the use of this material system in various photodetection applications.