Fabrication And Optical Characterization Of The CdZnTe And CdZnSe Coupled Quantum Structures

Recently, wide gap Ⅱ-Ⅵ compound semiconductors have been attracting much interest due to their applications in short-wave optoelectronic devices. Amongst these semiconductors, CdZnSe and CdZnTe alloy materials were paid more attention, wide emission bands of which cover the visible spectra range. It is more advantageous to realize energy band engineer by adjusting the alloy composition, the size oflow-dimensional structures, and coupling the low-dimensional structures.In this thesis, CdZnTe and CdZnSe alloy were grown and CdZnTe/ZnTe quantum wells with high quality were fabricated by metal organic chemical vapor deposition. In order to decrease the lifetime of excitons in quantum wells for obtaining an optical switch device, (CdZnTe/ZnSeTe)ZnTe complex quantum wells and CdZnSe quantum well/CdSe quantum dots complex structures were designed and fabricated. The optical properties of these structures were investigated. The following is the major results:1. The growth kinetics of the Cd_xZn_1-xTe alloy was studied. With keeping the flow rates of precursors, the Cd content in the epilayers decreases from 1 to 0 as the substrate temperature increases from 320℃ to 540℃. This reason was attributed to the difference on chemical stability and absorption property between dymethyl zinc and dymethyl cadmium.2. (CdZnTe,ZnSeTe)/ZnTe complex quantum wells were designed and fabricated. By means of shortening the lifetime of excitons in the CdZnTe well, faster turndown speed will be obtained. Single-exponential-fitting of the pump-probe result yields a down-time of 691 ±79 fs.3. CdZnSe/ZnSe self-assembled quantum dots were grown with S-K mode by MOCVD. With increasing CdZnSe thickness, the forming of quantum dots withthinning of wetting layer was observed via photoluminescence spectra.4. CdZnSe quantum well/CdSe quantum dots coupled structures were designed and fabricated. Photoluminescence measurements indicate that there exists efficient exciton tunneling from the CdZnSe quantum well to the CdSe quantum dots in the coupled structures.