Deep‐Level Transient Spectroscopy and Cathodoluminescence of CdSe/ZnSe QD Structures Grown on GaAs(100) by MBE

Abstract

b) P.N. Lebedev Physical Institute, RAS, 53 Leninsky Pr., CdSe/ZnSe structures grown on n þ -GaAs(100) by molecular beam epitaxy were studied by methods of deep-level transient spectroscopy (DLTS) and cathodoluminescence (CL). In DLTS measurements, an unusual dependence of the activation energy for electron emission from CdSe layer levels on filling conditions was observed. This dependence was explained on basis of the interaction between electron charge in CdSe quantum dots (QD) and charged deep levels placed in ZnSe barriers. The existence of barriers for the electron capture by QDs was found also.Introduction In the last years, thin CdSe layers in ZnSe crystal matrix have become the most popular system to study low dimensional structures in II-VI compounds. To date there are many articles devoted to investigations of structural and optical properties of CdSe/ZnSe QDs depending on growth conditions. However to our knowledge such structures have not been studied by the very informative DLTS method yet. In particular, DLTS allows to measure offsets of conduction and valence bands in quantum well (QW) structures [1, 2] that are very important information for potential device applications. In [3], the use of combined DLTS and photoluminescence measurements allowed to estimate an energy barrier for carriers at the InAs/GaAs interface of the QDs. Investigation of an influence of deep levels around the InAs QDs on carrier capture was carried out also by DLTS [4]. In this work we present first results of current-DLTS measurements of MBE-grown CdSe/ZnSe multilayer structures.

Study of structure and luminescence of CdSe Nanocrystals obtained by ball milling

“…Photoluminescence (PL) and CL investigations performed in these materials showed the appearance of luminescence bands at energies higher than the bulk band gap. In particular, Yamakawa et al 8 have reported a broad luminescence band centered at 2.49 eV in CdSe quantum dots of 15-40 nm in size grown by MBE, and Litvinov et al 17 have found similar bands peaked at 2.6 eV in quantum dots grown by the same technique. The emergence of these emissions in the visible range has been explained by quantum confinement effects.…”

High-efficient up-conversion of photoluminescence in CdSe quantum dots grown in ZnSe matrix

“…Firstly, the cation vacancy formation features A 2 B 6 semiconductors, and they cause a series of absorption and radiation bands in these materials [11]. Secondly, the deep traps for electrons were found in CdSe/ ZnSe structures with QDs by DLTS method [12]. And thirdly, it should be noted that in the case of the high density of QDs, when the distances between the islands are comparable with their size (for 1.5 ML the density of islands is ~ 10 11 cm 2 , and the average distance between them is 15-20 nm [1]), an elastic interaction between the islands becomes essential as a result of penetration of nonuniform strain field caused by the QDs into the substrate.…”

E-beam irradiation effect on CdSe/ZnSe QD formation by MBE: deep level transient spectroscopy and cathodoluminescence studies

“…To estimate a potential barrier height for electron capture in QDs we explored the dependence of the E1 and E1 * amplitudes for structure No. 281 on the relaxation time as described in [4,5,13]. These examinations allow us to determine a temperature dependence of capture cross section σ (T ) as [4]:…”