P. Boucaud et al., ABSORPTION AND EMISSION-SPECTROSCOPY OF INTERSUBBAND TRANSITIONS IN SI1-XGEX SI QUANTUM-WELLS/, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 16(3), 1998, pp. 1697-1700
An experimental study of the infrared properties of pseudomorphically
grown Si1-xGex quantum wells is presented. Undoped quantum wells grown
by ultrahigh vacuum chemical vapor deposition are investigated by pho
toinduced absorption and emission spectroscopies. The 2 nm thick Si0.7
Ge0.3 quantum wells exhibit infrared absorption around 10 mu m wavelen
gth which is associated with bound-to-continuum intersubband transitio
ns. We show that the study of photoinduced intersubband absorption giv
es valuable information on the dynamics of photocarriers. An average l
ifetime tau approximate to 2.5 mu s is deduced from the frequency depe
ndence of the photoinduced infrared absorption. We show that the tempe
rature dependence of the photoinduced absorption is governed by the th
ermal excitation of the carriers above the barriers. The infrared emis
sion of the quantum wells is studied in a second part. In III-V quantu
m wells, intersubband transitions around 10 mu m wavelength are clearl
y evidenced by room temperature infrared emission spectroscopy. In the
case of Si-SiGe quantum wells, only blackbody and defect-related emis
sions have been observed in the mid-infrared spectral range. The vanis
hing room-temperature emission is correlated with the weak photoinduce
d room-temperature absorption. (C) 1998 American Vacuum Society.