Pseudomorphic p-GexSi1-x/Si quantum-well infrared photodetectors for normal incidence operation between 20K and 77K

摘要

Abstract: Normal incidence spectral response and bias dependent responsivity measurements on p-type Ge$-x$/Si$-1$MIN@x$//Si quantum well infrared photodetectors reveal anomalous long wavelength photoresponse, extending out to 18 $mu@m depending on quantum well parameters. Room temperature FTIR absorptance measurements do not reveal significant absorption in this wavelength range; aside from the shorter wavelength intersubband optical transitions near 6 - 12 $mu@m in these Ge$-0.25$/Si$-0.75$/ quantum wells. Dark current induced filling of the higher-lying split-off hole state, with subsequent optical absorption, would give rise to infrared absorption in the 14 - 18 $mu@m range; however the split-off ground state to heavy-hole ground state lifetime required is $MIN@10 $mu@secs. In two-hole state structures having 300 angstroms barriers we observe dramatic increases in responsivity for bias voltage above 3 V, attributed to hot-hole transport enhancement of the photoconductive gain. This behavior is not observed in 500 angstroms barrier width structures.!12