The role of potential fluctuations in continuous-wave donor–acceptor pair luminescence of heavily doped materials

Abstract

It has recently become apparent that “standard” (low-concentration and low-compensation) theory for donor–acceptor pair (DAP) photoluminescence (PL) is totally incapable of explaining results in highly doped and compensated material. It can be noted that such material is often of high technological interest. It has been argued, mainly qualitatively, that the discrepancies result from potential fluctuations due to random ionic charges. We here present a quantitative theory for cw DAP PL, using an approximate model. We also present data for the concentration and intensity dependence of DAP PL in heavily doped ZnSe:N, and show that the results are explained very satisfactorily by our fluctuation model.

Optical properties of semiconductors with the Coulomb potential fluctuation: case of co‐doped ZnSe:(N,Cl)

“…All the PL spectra obtained from these samples at low excitation intensities are peaked well below 2.666 eV that corresponds to the lowest DAP emission energy for N acceptor and a "deep" donor associated with nitrogen doping [5]. Furthermore, in the samples with higher degree of compensation the recovery, if any, of phonon replicas occurs at higher excitation intensities, as expected from the theoretical prediction [4]. We note that we did recover phonon replicas in sample C under pulsed laser excitation.…”

“…The explanation to the observed behavior has been given previously based on the quasi-Fermi levels shifts [4] as well as due to screening effects [1][2][3][4]; both occur due to the increase in the concentration of neutral species caused by photogenerated carriers.…”

“…Refs. [1][2][3][4]). One of the most interesting and direct evidence about the presence of the Coulomb potential fluctuations as well as their effects on PL was given by Behringer et al [3] who studied co-doped ZnSe:Cl:N. Such an intentional simultaneous introduction of donors and acceptors allows one to vary the magnitude of the fluctuating potential in a somewhat controlled manner, which is important for our further discussions.…”

“…We present in this paper the experimental data on a series of similar co-doped ZnSe:Cl:N samples, which will clearly exhibit properties associated with the Coulomb potential fluctuations and which we shall describe qualitatively and, where possible, quantitatively, comparing with previously developed theories [2,4].…”

Selective excitation of the yellow and blue luminescence in n- and p-doped Gallium Nitride

“…These effects have been investigated by Kuskovsky, et al, by using a fixed excitation energy while changing the excitation intensity (I) in heavily N-doped ZnSe [119]. They found a nearly linear dependence of the DAP emission peak position on the log of excitation intensity in heavily doped materials:…”