Interplay between the hot phonon effect and intervalley scattering on the cooling rate of hot carriers in GaAs and InP

Abstract

The influence of hot phonon effect and intervalley scattering on the hot carrier cooling rate was investigated using femtosecond time‐resolved photoluminescence spectroscopy in bulk GaAs and InP, two electronically similar but vibrationally distinct semiconductors. In both materials, a broad photoluminescence signal that extends from the band gap energy to values larger than the pump pulse energy was observed during the first few picoseconds after photoexcitation, for different excitation energies (1.7, 1.88, and 2.4 eV) at high carrier densities (>1019 cm−3). Different hot carrier relaxation times were observed in GaAs and InP for different excitation energies, demonstrating the influence of intervalley scattering phenomena in GaAs. When electrons were not energetic enough to access satellite valleys, longer decay transients were observed for InP compared with GaAs. This provides experimental evidence of the hot phonon effect in InP. Temperature transients were calculated by analyzing the topography of the two‐dimensional spectra. Copyright © 2011 John Wiley & Sons, Ltd.

Hot carrier solar cell absorbers: materials, mechanisms and nanostructures

“…This has been shown in slowed carrier cooling for InN 10 as plotted in Fig. 2, and for slowed carrier cooling in InP compared to the small mass ratio GaAs, 11 as discussed below in section 4. Analogues of InN with abundant elements, but also with narrow E g are discussed below in Section 3.1.…”

“…The peak intensity (black arrows) can be seen to shift closer to the band gap (white lines) with time for both materials, but that for InP stays further above the band gap and at higher intensity for much longer times than that for GaAs. Figure 6: Hot carrier temperature relaxation for bulk GaAs and InP, redrawn from Clady et al 11 [Excitation and carrier density are the same as in Fig. 5.]…”

“…Furthermore issues related to differences of calibration of the detectors and non-linear crystal or of differences in chromatic losses of the optical setup are avoided. Figure 5: Time resolved PL spectra for bulk (a) GaAs and InP for 730 nm excitation wavelength redrawn from Clady et al 11 Carrier densities are 8.5x1019 cm-3. The peak intensity (black arrows) can be seen to shift closer to the band gap (white lines) with time for both materials, but that for InP stays further above the band gap and at higher intensity for much longer times than that for GaAs.…”

Hot carrier solar cell absorber prerequisites and candidate material systems

“…Slower carrier cooling has been observed in InP as compared to the small mass ratio GaAs [11]. Fitting of effective carrier temperature to time resolved photoluminescence data indicates approximately 300 1C higher carrier temperatures for InP at all times up 200 ps as compared to GaAs.…”

Requisites for Highly Efficient Hot-Carrier Solar Cells

“…Therefore, other nitride semiconductors are also the candidates. Clady et al compared InP and GaAs that have similar electronic band structures but different phononic properties [82]. Although InP has a phononic band gap not sufficiently wide to completely inhibit the Klemens decay, it exhibited a longer τ th than GaAs in which the atomic masses of the two constituent elements are very close to each other.…”