Molecular Beam Epitaxial Growth of AlN/GaN Multiple Quantum Wells
- PDF / 132,151 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 43 Downloads / 238 Views
L6.2.1
Molecular Beam Epitaxial Growth of AlN/GaN Multiple Quantum Wells Hong Wu, William J. Schaff, and Goutam Koley School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, U.S.A. Madalina Furis and A. N. Cartwright Department of Electrical Engineering, State University of New York at Buffalo, Buffalo, NY 14260, U.S.A. Karen A. Mkhoyan and John Silcox School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, U.S.A. Walter Henderson and W. Alan Doolittle School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332, U.S.A. A.V. Osinsky Science and Technology, Corning Inc., Corning, NY 14831, U.S.A. ABSTRACT AlN/GaN multiple quantum wells (MQWs) were grown on sapphire substrates by plasmaassisted molecular beam epitaxy. Growth temperature, III/V ratio, growth rate, and other growth parameters were optimized for the buffer layer and the MQWs, separately. The growth of AlN buffer was kept as Al-rich as possible while the formation of Al droplets was avoided. A GaN buffer layer was also tried but proved to be inferior to AlN buffer probably due to its larger surface roughness, higher dislocation density, and larger lattice mismatch with the AlN barrier layers in the MQWs. Very flat surfaces with a RMS roughness of 0.7nm were observed by atomic force microscopy (AFM) on the samples with both AlN buffer layer and 20 MQWs deposited under the optimized growth conditions. Abrupt interfaces and excellent periodicities of the MQWs were confirmed by X-ray diffraction (XRD) and reflectivity measurements with MQWs’ satellite peaks clearly visible up to the 10th order. Room-temperature intense ultraviolet (UV) photoluminescence (PL) emission with wavelength in the range of 320-350nm was also observed from the MQWs with well width ranging from 1.0 to 1.5nm. These MQW structures can potentially be used for UV light emitters and quantum cascade lasers. INTRODUCTION There have been considerable interests in group III-nitrides for their applications in the ultraviolet (UV) light emitter diodes (LEDs) and laser diodes (LDs) [1-3]. Until recently, most of the efforts had been focused on InGaN-based light emitters [1,2]. But to achieve light emission with even shorter wavelength, AlGaN-based light emitting structures need to be used. Due to the fact that low-dimensional heterostructures can provide carrier confinement and therefore
L6.2.2
improve the optical efficiency, AlGaN/GaN quantum wells with low aluminum concentration AlGaN barriers have been used to make UV LEDs [4]. In order to further shorten the emission wavelength, higher aluminum concentration AlGaN or even AlN barriers should be used in the quantum well structures. Besides the applications using intraband transitions, AlGaN/GaN quantum well system is also a potential candidate for quantum cascade lasers due to the recent realization of intersubband transitions (absorption, so far) [5]. High aluminum concentration AlGaN or AlN barriers are also needed in this case to maximize the inter
Data Loading...
