GaN/AIGaN intersubband optoelectronic devices (original) (raw)
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Mid-infrared quantum cascade detectors on InP
Infrared and Photoelectronic Imagers and Detector Devices II, 2006
ABSTRACT We report on the characteristics of two InP-based quantum cascade detectors (QCDs) whose responses are centered at 5.35 and 9 µm. The working principle is based on a vertical intersubband transition followed by a carefully designed extraction cascade, which is adapted to the LO-phonon energy. This device architecture leads to 10 K responsivities R of 8 and 26 mA/W and background limited detectivities D* BLIP of 1.7 x 10 10 and 0.9 x 10 10 jones, for the 5.35 µm and the 9 µm device, respectively. The temperature up to which background limited operation is seen is 115 K for the 5.35 µm device and roughly 65 K for the 9 µm detector. Designed for zero bias operation, QCDs produce a minimal dark current and therefore suffer very little from dark current noise. In addition, capacitance saturation at long integration times can be avoided, making them ideal devices for large focal plane arrays. The 5.35 µm detector was tested at high speed and room temperature. An optical beating signal generated by two slightly de-tuned singlemode quantum cascade lasers was used to test the detector's response at frequencies of up to 23 GHz.
Optics express, 2007
A fiber-optic pump-probe setup is used to demonstrate all-optical switching based on intersubband cross-absorption modulation in GaN/AlN quantum-well waveguides, with record low values of the required control pulse energy. In particular, a signal modulation depth of 10 dB is obtained with control pulse energies as small as 38 pJ. Such low power requirements for this class of materials are mainly ascribed to an optimized design of the waveguide structure. At the same time, the intersubband absorption fully recovers from the control-pulse-induced saturation on a picosecond time scale, so that these nonlinear waveguide devices are suitable for all-optical switching at bit rates of several hundred Gb/s.
This paper reviews the device physics and technology of optoelectronic devices based on semiconductors of the GaN family, operating in the spectral regions from deep UV to Terahertz. Such devices include LEDs, lasers, detectors, electroabsorption modulators and devices based on intersubband transitions in AlGaN quantum wells (QWs). After a brief history of the development of the field, we describe how the unique crystal structure, chemical bonding, and resulting spontaneous and piezoelectric polarizations in heterostructures affect the design, fabrication and performance of devices based on these materials. The heteroepitaxial growth and the formation and role of extended defects are addressed. The role of the chemical bonding in the formation of metallic contacts to this class of materials is also addressed. A detailed discussion is then presented on potential origins of the high performance of blue LEDs and poorer performance of green LEDs (green gap), as well as of the efficiency reduction of both blue and green LEDs at high injection current (efficiency droop). The relatively poor performance of deep-UV LEDs based on AlGaN alloys and methods to address the materials issues responsible are similarly addressed. Other devices whose state-of-the-art performance and materials-related issues are reviewed include violet-blue lasers, 'visible blind' and 'solar blind' detectors based on photoconductive and photovoltaic designs, and electroabsorption modulators based on bulk GaN or GaN/AlGaN QWs. Finally, we describe the basic physics of intersubband transitions in AlGaN QWs, and their applications to near-infrared and terahertz devices.