Optical study of interdiffusion in CdTe and ZnSe based quantum wells

Abstract

The interdiffusion in single quantum well structures was studied for a variety of II -VI semiconductor materials based on CdTe and ZnSe. In particular we have investigated CdTejCdMnTe, CdTejCdMgTe, HgxCdt_xTejHg y Cd t _ y Te and ZnSejCdZnSe structures in which an intermixing of column II elements can be induced as well as ZnSejZnSSe allowing an interdiffusion within the column VI sublattice. The diffusion was induced by rapid thermal annealing (RTA) for 1 min at different temperatures. The resulting blue shift of the characteristic emission spectrum was analyzed using photoluminescence spectroscopy. We observed a significant differencc of thc diffusion behavior between both groups of materials. While in all three CdTe based material systems an almost complete intcrdiffusion within the column II sublattice could be obtained at a high optical quality of the structures, both ZnSe based quantum wells show only remarkably small diffusion lengths. For all three CdTe based quantum wells we derived an activation energy of the interdiffusion process from a simple Fickian diffusion model applied to our measurements. We obtained a value of 2.8 eV for CdTejCdMnTe and CdTejCdMgTe and a value 2.1 eV for HgxCdt_xTejHgyCdl_yTe.Due to the fundamental role of diffusion for the production of semiconductor devices, the study of diffusion in semiconductor crystals has been of large interest in the last years. Self-diffusion or impurity diffusion in 111-V and 11-VI bulk materials was studied, e.g. by secondary ion mass spectroscopy (SIMS), a technique that allows a direct scanning of the diffusion profile [1]. In recent years, diffusion has also been investigated in thin heterostructures which offer an * Corresponding author.interesting source of concentration gradients. The interdiffusion of the materials in the well and barrier layers results in a blue shift of the emission spectrum [2]. The technological interest on this effect arises from the possibility to tune the wavelength of an optical emitter by simply annealing the device. On the other hand, it has been shown in III -V quantum .wells that the selective implantation of ions in a semiconductor heterostructure offers the possibility to define a lateral confinement [3,4]. Up to now the investigation of diffusion in heterostructures has been restricted mainly to 111-V materials. Only few 0022-0248/94/$07.00

Tunnel coupling in asymmetric semimagnetic double quantum wells

“…[10]). It shows different value of the activation energy [11] than that found in the comprehensive studies of the diffusion using delta-like markers in heterostructures without cap layer [12]. Some controversy concerns the fact that at particular conditions (cap thickness and structure parameters) the diffusion can be even suppressed [13].…”

“…3(a), is characteristic to the DMS QWs [14] and is attributed to excitons in the MW, which significantly lower their ground energy with increasing B. Bigger diffusion coefficient of the Mn as compared with the Mg [11] results in a higher concentration of Mn atoms in the MW and higher energy of exciton transition in the MW. Low relative intensity of this band is attributed to the non-radiative processes in in the MW due to Mn atoms, which are known as a source of non-radiative centers and defects [3].…”

Unique Temperature Dependence and Blinking Behavior of CdTe/CdSe (Core/Shell) Type-II Quantum Dots

“…We speculate this partially , where E a is the activation energy required for a single diffusion process within the crystal lattice. 37 CdTe/CdSe (C/S) heterostructures might partially form CdTeSe-alloyed structures at the core-shell boundaries when T is high. The alloyed structures may lead to exciton delocalizations and consequent band gap blue shifts.…”

Optical and structural studies of the effect of spacers in modulation-doped ZnSe/Zn1−xCdxSe quantum wells

“…[1][2][3] In particular, the studies of modulation-doped multiple quantum well structures ͑MD-MQWs͒ have been of great interest, since they are the basic components of many devices such as lasers. 1,2 Therefore, self-diffusion or impurity diffusion during the growth in heterostructures or device processing has been extensively studied with various techniques such as photoluminescence 4 and secondary-ion-mass spectrometry for III-V semiconductors.…”