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In nanostructure like quantum dots (QDs) embedded in the spacing layer with high energy barrier, where electrons are three-dimensionally confined into nanometer-scale semiconductor structures, the novel physical characteristics are expected to emerge. The novel properties would greatly improve semiconductor device performance. Optoelectronic devices with quantum dot heterostructure like quantum dot infrared photodetector (QDIP) have already been proposed in the recent years. When QDs are incorporated into the layered structure of a semiconductor for optoelectronic device applications, electrical control is critical to the operation of device. It is desirable that both an electric field can be applied to change physical properties of the QDs embedded in the spacing layers i.e., the active region of the device and that the photo-induced carriers can be excited and transited to generate the photocurrent. In this chapter, The pseudopotential model of using multiple-quantumdot (MQD) structures for detect infrared radiation can be explained by exploiting the basic principles of quantum mechanics, with the uniform and isotropic strain-induced potential to well simulate the electronic properties of InAs/In(Ga)As QDIP active region by finite element method (FEM). The vertically coupled and decoupled wave-functions of electrons on MQD with dependences of thickness of spacing layers are also calculated by means of the FEM. The method is ideally suited for numerical analysis by computer. The typical and particular QDIP structure are involved and introduced in this section. Here, the outstanding performance of the QDIP which has emerged as a potential alternative to QWIPs would be proposed. The motivation for interest in QDIPs is rooted in two characteristics of quantum dots. The first is that QDIPs are sensitive to normal-incident infrared radiation, a consequence of the 3-D confinement of electrons in the quantum dots. The other attribute is the weak thermionic coupling between the ground state and excited states. This should result in lower thermal excitation and, thus, lower dark current and higher operating temperature. The concomitant increase in the lifetimes of excited carriers should enable higher responsivities as carriers have more time to escape and contribute to the 13

In this study, we study a heat transfer model, with the surface of the microbolometer device receiving radiation from blackbody constructed using a COMSOL Multiphysics simulator. We have proposed three kinds of L-type 2-leg and 4-leg with the pixel pitch of 35 &mu, m based on vanadium oxide absorbent membrane sandwiched with top passivated and bottom Si3N4 supporting films, respectively. Under the blackbody radiation, the surface temperature changes and distributions of these samples are simulated and analyzed in detail. The trend of change of the temperature dependent resistance of the four kinds of bolometer devices using the proposed heat transfer model is consistent with the actual results of the change of resistance of 4 samples irradiated with 325 K blackbody located in the front distance of 5 cm. In this paper, &Delta, T indicates the averaged differences of the top temperature on the suspended membrane and the lowest temperature on the post of legs of the microbolometers. It is shown that &Delta, T &asymp, 17 mK is larger in nominal 2-leg microbolometer device than that of 4-leg one and of 2-leg with 2 &mu, m &times, 2 &mu, m central square hole and two 7.5 &mu, m slits in suspended films. Additionally, only &Delta, 5 mK with 4-leg microbolometer device under the same radiated energy of 325 K blackbody results from the larger total thermal conductance.

The ten stacked self-assembled InAs/GaAs quantum dot infrared photodetectors (QDIP) with different Al/sub 0.3/Ga/sub 0.7/As barrier widths and growth temperatures were prepared. Asymmetric current-voltage (I-V) characteristics and 2/spl sim/7.5 /spl mu/m detection window were observed. Peak responsivity of 84 mA/W at -0.4 V and peak specific detectivity of 2.5/spl times/10/sup 9/ cm-Hz/sup 1/2//W at zero bias were observed at 50 K. The characteristics of polarization insensitivity over the incident light and the high background photocurrent suggest that the self-assembled QDIP can be operated at higher temperature (/spl sim/250 K) under normal incidence condition in contrast to quantum well infrared photodetector (QWIP).

I – V characteristics of the unpassivated InAs p–i–n diodes with various i-layer thickness have been systematically studied. At the same reverse bias of −0.5 V, the reverse current density is −0.83 and −0.18 A/cm 2 for the p–n diodes and p–i–n diodes with a 0.72-μm-thick i-layer, respectively. It is obvious that the surface shunt and bulk leakage current are dramatically decreased owing to increasing of the i-layer thickness between p and n layers of InAs p–n junction. Meanwhile, an odd current–temperature behavior; the reverse-bias current decreases with increasing temperature, has been observed in the InAs p–i–n photodetector with a 0.72-μm-thick i-layer. Below 90 K, the photocurrent generated by the background thermal radiation should dominate the I – V characteristics of the p–i–n diode and the photocurrent increases a little as temperature drops due to the improvement of minority carrier diffusion length.

An unpassivated InAs p-i-n photodetector with excellent performance at room temperature was demonstrated. The zero-bias resistance area products of the diode with 720-nm thick i-layer are 8.1 /spl Omega/-cm/sup 2/ at room temperature and as high as 1.3 M /spl Omega/-cm/sup 2/ at 77 K. At 77 K, the diode exhibits a breakdown voltage exceeding 13 V. When tested under a 500 K blackbody source, the measured detectivity limited by Johnson noise is 1.2/spl times/10/sup 10/ cm-Hz/sup 1/2 //W at room temperature and 8.1/spl times/10/sup 11/ cm-Hz/sup 1/2 //W at 77 K. To our knowledge, this is the best data for a room temperature infrared detector.

A ten-stacked self-assembled InAs/GaAs quantum-dot infrared photodetector operated in the 2.5–7 μm range by photovoltaic and photoconductive mixed-mode near-room-temperature operation (⩾250 K) was demonstrated. The specific peak detectivity D* is 2.4×108 cm Hz1/2/W at 250 K. The use of high-band-gap Al0.3Ga0.7As barriers at both sides of the InAs quantum-dot structure and the long carrier recombination time are the key factors responsible for its near-room-temperature operation.

The InAs/GaAs quantum dot (QD) edge light emitting diode (LED) emitting at a wavelength of 1 /spl mu/m has been fabricated which exhibits very small wavelength shift of 0.22 nm/K and the full width at half maximum (FWHM) broadening shift of 0.04 nm/K. Detailed temperature characteristics over a range from 20 to 300 K are presented.

In this letter, the effect of extraordinary transmission of periodic metal hole arrays is directly integrated into the quantum dot infrared photodetector with broadband response. It is found that the detector response is strongly modulated by the extraordinary transmission from the excitation of surface plasmon.

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The temperature-dependent capacitance–voltage (C–V) characteristics of two stacked InAs/GaAs quantum dot p–i–n diode were investigated. The capacitance discontinuities observed are attributed to charge storage in the InAs quantum dots. The average storage electrons at each InAs quantum dot thus obtained are two and three electrons at room temperature and at temperature below 100 K, respectively. In the intermediate temperature range from 100 to 250 K, fractional charge occupation is observed in each dot. When the C–V measurement frequency is lowered from 800 to 80 kHz, the capacitance turns into a negative value under low biases which indicates the dominance of the inductance at lower frequency.

The current leakages of InAs photodiodes have been systematically studied by adding undoped layers having thicknesses of 0, 0.30, and 0.72 μm between the p–n junction. At reverse bias V=−0.5 V, the dark currents of the InAs p–i–n diodes with undoped layer thicknesses of 0, 0.30, and 0.72 μm are about 5×10−6, 7×10−8, and 1×10−10 A, respectively, at 77 K. The leakage current of the InAs p–n diode was successfully reduced by adding 0.72-μm-thick undoped layer between the p–n junction.