Epitaxial Structures For Optical Information Processing Applications: Superlattice Infrared Detectors
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EPITAXIAL STRUCTURES FOR OPTICAL INFORMATION PROCESSING APPLICATIONS: SUPERLATTICE INFRARED DETECTORS
MOSES T. ASOM AT&T Bell Laboratories, Solid State Technology Center, Breiningsville PA 18031 ABSTRACT
Advances in epitaxial growth techniques such as molecular beam epitaxy and metal organic chemical vapor deposition have facilitated the formation of high quality III-V heterostructures with dimensional control down to atomic levels, with abrupt doping and near-defect-free interfaces. The flexibility and remarkable control offered by these techniques have resulted in the fabrication of new devices based on confinement or modulation of carriers in thin III-V heterostructures. Quantum wells and superlattice based devices are expected to be utilized in optical information processing as sources, modulators, and detectors. In this paper, we will review the general epitaxial requirements for quantum wells and superlattices based devices, and discuss the fabrication and properties of a new class of infrared photodetectors that employ intraband transitions in quantum wells.
INTRODUCTION Artificial structuring of II1-V compound semiconductors has been achieved because of the progress made in epitaxial growth techniques such as molecular beam epitaxy (MBE), gas source molecular beam epitaxy (GSMBE) and metal organic chemical vapor deposition (MOCVD). These techniques, especially MBE and GSMBE, offer unprecedented control of epitaxial thickness, alloy composition, doping, and interface quality [1]. The control offered by MBE has resulted in the realization of novel III-V semiconductor structures such as quantum wells (QW) and superlattices (SL) [2]. One method of forming QW and SL is by growing a low-band gap material (e.g GaAs) between two wide-band gap materials (e.g AlxGalixAs). Carriers are confined in the low bandgap material (well) and discrete energy levels are formed in the well. The confinement of carriers in the well is the basis for utilization of QW and SL in the fabrication of devices for optical information processing in specific areas such as optical computing, photonic switching, optical and infrared detection. Some of the devices currently suitable for these applications include the surface emitting lasers (SELs) [3,4], self electro-optic effect devices (SEED) [5], avalanche photodetectors [6] and long wavelength quantum well infrared photodetectors (QWIP) [7]. In the next section we will discuss the general requirements in the epitaxial growth of quantum wells and superlattices and present optical measurements on short period superlattice structures. The remainder of the paper will concentrate on molecular beam epitaxial growth, characterization, fabrication, and performance of long wavelength infrared photodetectors based on intersubband transition in GaAs/A1GaAs QW.
Mat. Res. Soc. Symp. Proc. Vol. 228. (1992 Materials Research Society
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EPITAXIAL REQUIREMENT FOR I1-V PHOTONICDEVICES Growth of QW and SL for optical information processing devices require the control of thickness, doping, alloy compos
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