Photoluminescence and infrared transmission spectroscopies of

Abstract

The first detailed photoluminescence (PL) study of as-grown CdGeAs 2 samples obtained from three different sources is presented. The study was carried out in the 5-100 K temperature range and laser excitation densities 0.5-5 W cm −2 . PL spectra collected on samples from all sources showed a PL band near 355 meV which is assigned to an (e, A 0 ) transition to the deep native double acceptor 315 meV above the valence band edge. Samples from one source which contained substantially lower levels of oxygen also had about an order of magnitude lower values of absorption coefficient below the band gap and showed also a single PL band in their PL spectra.

Improving optical transparency in CdGeAs2 crystals by controlling crystalline defects

“…CGA with moderate to high optical absorption has generally been found to exhibit two photoluminescence (PL) bands at 0.35 and 0.55 eV, respectively [12][13][14]. The band at 0.35 eV has been assigned to a transition from a shallow donor to a deep acceptor [12,14,15].…”

“…The band at 0.35 eV has been assigned to a transition from a shallow donor to a deep acceptor [12,14,15]. The PL band at 0.55 eV, which is not present in highly transparent material, has been suggested to be related to a donorshallow acceptor pair recombination process [12][13][14]. Optical absorption at 5.5 mm, which has varied between 0.4 [11] and 18.4 cm À1 [16], has been attributed, based in part on PL data, to be intraband transitions between the two upper valence bands [17,18].…”

Luminescence study of donors and acceptors in CdGeAs2

“…Photoluminescence studies [7][8][9] of bulk CdGeAs 2 crystals have revealed two dominant PL emission bands. One broad band centered near 0.35-0.38 eV has been assigned as either donor-acceptor-pair (DAP) recombination [8], or an (e, A 0 ) transition involving a deep native double acceptor [9].…”

“…One broad band centered near 0.35-0.38 eV has been assigned as either donor-acceptor-pair (DAP) recombination [8], or an (e, A 0 ) transition involving a deep native double acceptor [9]. A second band peaking near 0.55 eV was found to shift to high energy with increasing excitation intensity, and it has been observed to shift by tens of meV when the laser spot was scanned across the sample [8,9], although the origin of the shift was not determined. The 0.55-eV band was suggested to be a DAP transition at low temperatures [7][8][9], converting to conduction band-valence band (e, h) recombination for T > 100 K [8].…”

“…A second band peaking near 0.55 eV was found to shift to high energy with increasing excitation intensity, and it has been observed to shift by tens of meV when the laser spot was scanned across the sample [8,9], although the origin of the shift was not determined. The 0.55-eV band was suggested to be a DAP transition at low temperatures [7][8][9], converting to conduction band-valence band (e, h) recombination for T > 100 K [8]. In our previous work [7], we observed this PL band only in samples with significant absorption at 5.5 lm, and suggested that the acceptor center was the same shallow defect that was responsible for the p-type conduction.…”