Novel Materials and Technologies for IR Optoelectronic Applications
Doctoral thesis, 2012
This thesis focuses on novel III-V materials (InAs/GaSb type-II superlattices, T2SL, and dilute bismides) and metamorphic growth techniques for infrared optoelectronics all of which may find wide spread applications in telecommunication, energy harvesting and saving, sensing and imaging. Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) photodetectors at the atmospheric windows of 3-5 and 8-12 µm, respectively, are currently dominated by HgCdTe and quantum well infrared photodetectors. These detectors, however, suffer from the suitability for making focal plane array (FPA) detectors due to the material non-uniformity or the low operation temperature that significantly increases the cost for a practical detection or imaging system. InAs/GaSb type-II superlattices are promising candidates for FPA detectors with better performance at a lower cost. Dilute bismides where a small amount of Bi atoms are incorporated into traditional host III-V semiconductors have theoretically shown a number of interesting physical properties. The large energy band bowing effect with retained transport and optical properties make these materials attractive for making short-wavelength infrared (SWIR), MWIR and LWIR optoelectronic devices. Dilute bismides have been only little studied among the III-V semiconductors, and in particular epitaxial growth of dilute III-SbBi is almost unexplored. Metamorphic growth is an efficient technique for lattice engineering and useful for device applications such as multi-junction solar cells, III-V and Si integration, electronic and optoelectronic devices on cheap substrates. Here, growth optimization and innovations to minimize threading dislocations are challenging and crucial for improving the material quality.
The work in this thesis deals with issues related to the realization of these novel III-V materials and metamorphic growth techniques using molecular beam epitaxy (MBE). It is investigated how doping in alloy graded metamorphic buffers influences material quality and a new method to reduce dislocation density and improve optical quality by using dilute nitride buffer layers is demonstrated. Design and growth optimization of T2SL structures for mid-IR detectors are presented. MBE growth of novel dilute III-SbBi alloys is investigated. The growth of GaSbBi is reported for the first time. The abnormal lattice contraction of GaSbBi is discovered and explained.
InAs/GaSb type-II superlattice
alloy graded buffer
molecular beam epitaxy
Kollektorn (A423) at the Department of Microtechnology and Nanoscience (MC2), Kemivägen 9, Göteborg
Opponent: Professor Eric Tournie, Electric Engineering and Electronics Department, Université Montpellier 2-CNRS, France.