Stimulated and spontaneous far infra-red emission from uniaxially strained gapless Hg1-xCdxTe |
Maxym Strikha ^{1}, Georgiy Shepelskii ^{}, Salim Gasan-zade ^{} |
1. Institute for Physics of Semiconductors of NAS of Ukraine, 45 Prospekt Nauki, Kyiv 03028, Ukraine |
Abstract |
The intensive far IR irradiation in the range of 80-100 mkm was observed in uniaxially strained gapless p-Hg1-xCdxTe in the strong electric field. The transformation of energy spectrum of gapless semiconductor (GS) occuring under uniaxial strain P is following: the energy gap is formed between the c- and v-bands at k=0. The gap width is proportional to P. The v-band has loop-like top in the plane, transverse to deformation direction. The resonance acceptor level in GS splits under strain also. The lower of two split levels moves in the gap, and then, at P=2.5 kbar, it becomes resonance in the v-band. The inverse occupation in strained Hg1-xCdxTe is created because the hot electrons distribution occurs in the c-band under impact ionization, while the holes are localized near the v-band top. The band-to-band radiation transition occurs only at phonon participation, therefore its probability is low. The probability of this transition increases dramatically (by orders of magnitude) when the acceptor level becomes resonance in the v-band. Therefore, the stimulated irradiation can take place. Experimentally this effect was observed in p-Hg1-xCdxTe (x=0.10-0.14), at T=4.2 K in the pulse electrical fields E<60 V/cm and at P<3 kbar. At threshold values of strain and electric field (P=2.5-2.7 kbar, E=50-55 V/cm), the dramatic increase of irradiation (by 3 orders of magnitude) and the increase of current (by 4-6 times) occurs. The existence of thresholds in E and P values, the great intensity of signal, and the correlation between radiation and current signals, points to stimulated character of the emission. |
Presentation: Oral at E-MRS Fall Meeting 2009, Symposium D, by Maxym Strikha Submitted: 2009-05-20 13:13 Revised: 2009-06-07 00:48 |