Photoluminescence characterization of cubic CdS epilayers

Abstract

PACS 71. 78.55.Et Cubic CdS epilayers were grown on (100) GaAs substrates by hot-wall epitaxy and their photoluminescence (PL) characteristics were studied. A heavy hole free exciton peak was observed even at room temperature and a light hole free exciton peak was observed at 30 -100 K. The temperature dependence of the free excitonic emission intensity was demonstrated using a two-step quenching mechanism. The excitation power dependence showed that the PL peak at 2.367 eV is due to the free-to-bound transition.1 Introduction Cadmium sulfide is a semiconductor with a wide and direct band gap. It has been studied for application in heterojunction photovoltaic devices along with other II-VI semiconductor materials [1]. CdS has two structures: a stable hexagonal wurtzite structure and a metastable cubic sphalerite structure. Most studies have been conducted on hexagonal CdS, whereas there has been little reported research on cubic CdS since the production of high quality cubic CdS is difficult.To date, cubic CdS epilayers have been grown on InP or GaAs substrates [2][3][4][5]. Some research on cubic CdS optical properties [6][7][8][9], free excitons by photoluminescence (PL), and reflection [10-13] has been reported. Studies have also been carried out to grow cubic CdS-based low-dimensional quantum structures for opto-electronic devices [14]. Recently, we studied the room-temperature energy gap and the binding energy of the free exciton by absorption and PL [15,16].In this work, PL spectra in cubic CdS grown by hot-wall epitaxy (HWE) were extensively studied. The existence of stacking faults in the CdS epilayer was examined using reciprocal space mapping (RSM). The temperature and excitation power dependencies of the near band edge emissions were also investigated.

Raman Spectroscopy of Ultranarrow CdS Nanostructures

“…A similar increase in the low-energy surface state emission intensity upon cooling was reported earlier 33 and assigned to defects and irregularities in the samples. For the cubic phase of CdS, 34 the opposite behavior was reported, where sample cooling caused narrowing of the photoluminescence peaks along with a blue shift.…”

New cubic Cd1−xMnxS epilayers grown on GaAs (100) substrates by hot-wall epitaxy

“…The pure cubic CdS spectrum has been discussed in detail elsewhere. 11,12,40 In spite of very low Mn composition of x = 0.020 and 0.030, no other peaks such as an appreciable near-edge emission peak and SA peak, shown in the pure CdS PL spectrum, were observed in the higher energy region of 2.2 to 2.5 eV. Only one broad and strong emission peak labeled as A was observed.…”

Paths for the Non-radiative Recombination Occurring in CdS:CdO/Si Multi-Interface Nanoheterostructure Array

“…It is found that with temperature increasing, the PL peak intensity decreases slowly below 50 K, while exponentially after that till 300 K. This phenomenon suggests that there exist two different non-radiative recombination paths in as-prepared CdS:CdO/Si-NPA, which independently lead to the PL quenching in different temperature ranges. [24] By taking into account a two-step quenching mechanism, the PL intensity as a function of temperature can be expressed as [24] 𝐼(𝑇…”

“…This suggests that the PL quenching occurring at the low temperature range (below 50 K) should be attributed to the thermally activated transition between the heavy hole and the light hole, with an energy requirement of ∼10-12 meV. [24,27] Beyond 50 K, the main non-radiative process responsible to the PL quenching might be due to the thermal escape from the structural defects assisted by scattering with longitudinal optical (LO) phonons. [23] According to the fitted value (Table 1), the activation energy is ∼66.7 meV.…”