Nonequilibrium phonon dynamics and electron distribution functions in InP and InAs

Abstract

We have used subpicosecond laser pulses to study the generation of nonequilibrium LO phonons in both InP and InAs. These two semiconductors provide a contrast in that the decaying of the Raman signal probes different relaxation mechanisms. In InP, for example, we find that the decay of the Raman signal is dominated by the lifetime of the LO phonons. On the contrary, in InAs, our studies show that the decay of the Raman signal is governed by the time required for electrons to return to the ⌫ valley from the L valleys of the conduction bands. In addition, nonequilibrium electron distributions were also studied in InP and InAs. We have found that the single-particle-scattering spectrum in InAs can only be observed with the use of a much longer laser pulse width than subpicosecond as a result of electron intervalley scattering and very small electron effective mass.

Hot electron effects in ultra‐short gate length InAs/InAlAs HEMTs

“…In this case, the average electron energy is sustained along the drain end of the channel. This is because the relaxation time of carriers returning from satellite valleys is quite long in InAs and presumably also in strained In 0.75 Ga 0.25 As [11]. This effect becomes even more pronounced at smaller source-to-drain spacings because the distance over which relaxation can occur is further reduced.…”

Numerical analysis of the relaxation of photoexcited carriers and the hot-phonon effect in GaN

“…Our aim is to investigate the influence of the electrons and holes effective mass on the carrier's cooling rate. Considering that there is no information available on the relaxation time for GaN, we assume in our calculations some values relative to other semiconductors obtained from published data, namely: t LO ¼ 1:0 ps [36] (CdSe), t LO ¼ 1:8 ps [10] (InAs), t LO ¼ 2:3 ps [10] (InP) and t LO ¼ 7:0 ps [10] (GaAs). We choose the mode corresponding to the wave number 3 Â 10 6 cm À1 whose temporal evolution is shown in Fig.…”

“…Furthermore, it is well-known that the highly excited carriers rapidly relax energy toward the LO-phonon system, creating large nonequilibrium phonon populations. A build-up of the nonequilibrium phonons creates a bottleneck in the relaxation channel carrier-phonon LO that may influence considerably the carriers' cooling rate [2,[5][6][7][8][9][10][11]. The diminished effectiveness of the process of relaxation in the carrier system, with an accompanied slowing down in the rate of energy loss has been mainly ascribed to this so-called hotphonon effect [12].…”

Semicontinuous Kinetic Theory of the Relaxation of Electrons in GaAs

“…Further, we specialize our model equations to a system of free electons interacting with acoustic phonons treated in the Debey approximation and optical phonons with a constant phonon energy (Einstein model) (Ashcroft and Mermin 1976). Numerically, we study the relaxation of an electron gas interacting with the phonons in the polar semiconductor gallium arsenide (Lugli et al 1989;Grann, Tsen, and Ferry 1996;Supancic et al 1996). In particular we investigate the influence of hot phonons on the electronic system.…”