Kazuhiro Nagase

InAs deep quantum well structures and their application to Hall elements

Abstract We have investigated new InAs deep quantum well structures (InAs DQWs) made from InAs/AlGaAsSb materials on GaAs substrates by molecular beam epitaxy (MBE). In the InAs DQWs, AlGaAsSb layers are lattice matched to InAs. High electron mobilities of more than 20000 cm 2 / V · s at room temperature have been obtained in a wide range of substrate temperature and Al composition of Al x Ga 1− x AsSb layers (0 ≤ x ≤ 0.8). The InAs DQWs have been applied to Hall elements (HEs) for the first time. The new type of HEs with InAs DQWs (InAs DQWHEs) show superior characteristics, such as output voltage as high as 520 mV (at V in = 6 V , B = 0.1 T ), small dependence of input resistance on temperature and good reliability for practical use.

AlGaAsSb buffer/barrier on GaAs substrate for InAs channel devices with high electron mobility and practical reliability

InAs/AlGaAsSb deep quantum well was successfully formed on GaAs substrate and examined for two electron devices, Hall elements (HEs), and field-effect transistors (FETs). With a thin buffer layer of 600 nm AIGaAsSb on GaAs substrate, we observed high electron mobility more than 23000 cm2/Vs and extrinsic effective electron velocity of 2.2 x 107 cm/s for a 15 nm thick InAs channel at room temperature. AIGaAsSb lattice matched to InAs was discussed from the view points of insulating property, carrier confinement, and oxidization rate. Reliability data good enough for practical use were also obtained for HEs. We demonstrated AIGaAsSb as a promising buffer/barrier layers for InAs channel devices on GaAs substrate, and we discussed the possible advantages of AIGaAsSb also for InGaAs FETs.

High sensitivity Hall elements made from Si-doped InAs on GaAs substrates by molecular beam epitaxy

Abstract We have newly developed Hall elements consisting of Si-doped InAs thin film grown on GaAs substrate by molecular beam epitaxy (MBE). By doping Si into the layer of InAs thin films far from the InAs/GaAs interface, InAs thin films with high electron mobility are obtained and temperature dependent variations of the electron mobility and sheet resistance are much reduced. These InAs thin films were processed into Hall elements with practically useful characteristics.

Miniaturized InSb photovoltaic infrared sensor operating at room temperature

This paper reports the development of a novel InSb photovoltaic infrared sensor (InSb PVS) operating at room temperature. The InSb PVS consists of an InSb p+/p-/n+ structure grown on semi-insulating GaAs (100) substrate, with a p+ Al0.17In0.83Sb barrier layer between p+ and p- layers to reduce diffusion of photo-excited electrons. Photodiodes were fabricated by wet etching process and, using a 500K blackbody, we obtained D* of 2.8x108 cmHz1/2/W and RV of 1.9 kV/W at room temperature. S/N was improved with the serial connection of 700 photodiodes patterned on a 600x600 μm2 chip. Increasing the number (N) of connected photodiodes, S/N ratio was improved by a factor of N1/2. RV was constant for signals ranging from DC to 500Hz. From spectral response measurements a cut-off wavelength of 6.8 μm was obtained. The InSb PVS was flip-chip bonded on a pre-amplifier IC, allowing the shortest connection between the InSb PVS and the pre-amplifier, making the system immune to electromagnetic noise. The system was finally encapsulated by a Dual Flat Non-leaded (DFN) package with a window, which exposes the backside of the GaAs substrate allowing the infrared light incidence. The device external sizes are 2.2 mm x 2.7 mm x 0.7 mm and to our knowledge is the smallest uncooled sensor for the middle-infrared range reported until now.

A Novel InSb Photodiode Infrared Sensor Operating at Room Temperature

A microchip-sized InSb photodiode based infrared sensor (InSb PDS) that operates at room temperature was developed. The InSb PDS consists of 700 photodiodes connected in series and consumes no power, because it works in photovoltaic mode to output an open-circuit voltage. The InSb PDS has a typical responsivity of 1,900 V/W and an output noise of 0.15 μV/Hz 1/2 . A detectivity of 2.8×10 8 cmHz 1/2 /W was obtained at 300 K. The InSb PDS has performance high enough for applications such as mobile electronic equipment, personal computers, and consumer electronics

High-performance solar-blind Al0.6Ga0.4N/Al0.5Ga0.5N MSM type photodetector

An Al0.6Ga0.4N/Al0.5Ga0.5N metal–semiconductor–metal (MSM) deep-ultraviolet (DUV) photodetector was developed. It possesses both high photosensitivity and high rejection ratios in comparison to photomultiplier tubes (PMTs). The photodetector was designed to have a two-dimensional electron gas layer at the Al0.6Ga0.4N/Al0.5Ga0.5N hetero-interface, which plays an important role in increasing the photosensitivity. Additionally, for reducing the dark current, a V/Al/Mo/Au electrode was employed as a Schottky electrode with an appropriate barrier height. Upon irradiation with 10 μW/cm2, an extremely low dark current (10−11 A) and high photocurrent (5 × 10−5 A) were achieved at a bias voltage of 5 V. The photodetector was true solar-blind with a cut-off wavelength of 280 nm. A high photosensitivity of 106 A/W and a rejection ratio of 106 were realized under the irradiation of 10 nW/cm2 DUV photons. The present results revealed that the AlGaN/AlGaN MSM DUV photodetector is one of the most suitable candidates for...