GaSb-based materials can be used to produce high performance photonic devices operating in the technologically important mid-infrared spectral range. Direct epitaxial growth of GaSb on silicon (Si) is an attractive method to reduce manufacturing costs and opens the possibility of new applications, such as lab-on-a-chip MIR photonic integrated circuits and monolithic integration of focal plane arrays (FPAs) with Si readout integrated circuits (ROICs). However, fundamental material dissimilarities, such as the large lattice mismatch, polar-nonpolar character of the III-V/Si interface and differences in thermal expansion coefficients lead to the formation of threading dislocations and antiphase domains, which effect the device performance. This work reports on the molecular beam epitaxial growth of high quality GaSb-based materials and devices onto Si. This was achieved using a novel growth procedure consisting of an efficient AlSb interfacial misfit array, a two-step GaSb growth temperature procedure and a series of dislocation filter superlattices, resulting in a low defect density, anti-phase domain free GaSb buffer layer on Si. A nBn barrier photodetector based on a type-II InAs/InAsSb superlattice was grown on top of the buffer layer. The device exhibited an extended 50 % cut-off wavelength at 5.40 μm at 200 K which moved to 5.9 μm at 300 K. A specific detectivity of 1.5 x1010 Jones was measured, corresponding in an external quantum efficiency of 25.6 % at 200 K.
In this work, we report interband cascade light emitting diodes (ICLEDs) based on InAs/GaAsSb superlattices emitting around 4.5 μm The ICLED structures were grown on InAs substrates by molecular beam epitaxy, which were composed of InAs/GaAsSb superlattice emitters, InAs/AlAsSb multi-quantum well (MQW) injection regions, and the GaAsSb/AlAsSb MQW tunneling regions. Both 5-stage and 2-stage ICLEDs were fabricated. The devices exhibited high output power, low series resistance and high wall-plug efficiency (WPE). At room temperature, radiances of 0.36 W/cm2 sr and 0.19 W/cm2 sr were achieved from the 5-stage and 2-stage ICLEDs respectively. At 80 K, the output power from the 5-stage ICLED reached 3.56 mW with 350 mA injection current, resulting in a WPE of around 0.5%. The efficiency was largely maintained with increasing injection. The thermal quenching of these ICLEDs from 20 K to 300 K was also significantly less than other types of devices emitting at similar wavelengths. These results demonstrate that ICLEDs have great potential for mid-infrared light emitting diode applications requiring large output power and high wall-plug efficiency.
Novel InSb quantum dot (QD) nanostructures grown by molecular beam epitaxy (MBE) are investigated in order to improve the performance of light sources and detectors for the technologically important mid-infrared (2-5 μm) spectral range. Unlike the InAs/GaAs system which has a similar lattice mismatch, the growth of InSb/InAs QDs by MBE is a challenging task due to Sb segregation and surfactant effects. These problems can be overcome by using an Sb-As exchange growth technique to realize uniform, dense arrays (dot density ~1012 cm-2) of extremely small (mean diameter ~2.5 nm) InSb submonolayer QDs in InAs. Light emitting diodes (LEDs) containing ten layers of InSb QDs exhibit bright electroluminescence peaking at 3.8 μm at room temperature. These devices show superior temperature quenching compared with bulk and quantum well (QW) LEDs due to a reduction in Auger recombination. We also report the growth of InSb QDs in InAs/AlAsSb ‘W’ QWs grown on GaSb substrates which are designed to increase the electron-hole (e-h) wavefunction overlap to ~75%. These samples exhibit very good structural quality and photoluminescence peaking near 3.0 μm at low temperatures.