Intersubband Quantum Well Photodetector ( QWIP ) (original) (raw)
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3 m m Intersubband Quantum Well Photodetector (QWIP)
In recent years photodetectors operating in the mid- to far infrared region of 3-15 m m have been designed based on electron and hole intersubband transitions in multiple quantum wells and superlattices. In general, QWIPs based on electron transitions show greater detectivity compared to the hole-based photodetectors. However, selection rules for electron intersubband transitions usually forbid the TE mode operation, associated with normal light incidence; Therefore, special coupling structures/geometries have been employed to couple light into the device. The spectral region 3-5 m m is of interest for a variety of applications such as environmental gas sensing, thermal imaging etc. and is not well covered by existing detectors. We have grown a QWIP operating at ˜ 3m m with a normal incidence component which incorporates an InGaAs/GaAs asymmetric quantum well from which photo-excited carriers undergo resonant tunnelling into the AlGaAs barriers. A study of temperature-dependent dark...
Ultimate performance of quantum well infrared photodetectors in the tunneling regime
Infrared Physics & Technology, 2009
Thanks to their wavelength diversity and to their excellent uniformity, Quantum Well Infrared Photodetectors (QWIP) emerge as potential candidates for astronomical or defense applications in the very long wavelength infrared (VLWIR) spectral domain. However, these applications deal with very low backgrounds and are very stringent on dark current requirements. In this paper, we present the full electro-optical characterization of a 15µm QWIP, with emphasis on the dark current measurements. Data exhibit striking features, such as a plateau regime in the I(V) curves at low temperature (4 to 25 K). We show that present theories fail to describe this phenomenon and establish the need for a fully microscopic approach.
IEEE Transactions on Electron Devices, 2000
It is well known that the hole intersubband absorption of normally incident (TE polarized) radiation is nonzero for p-doped quantum well infrared photodetectors (p-QWIP's) which have been fabricated without an optical grating. This present paper shows from theory that, for typical p-QWIP designs, this hole intersubband absorption of TE polarized radiation (without the help of an optical grating) is significantly smaller than the electron intersubband absorption of TE polarized radiation in those n-doped QWIP's (n-QWIP's) fabricated with an optical grating.
IEEE Journal of Quantum Electronics, 2000
In this paper, we propose a system based on GaAs heterostructure where it is possible to generate photocurrent with mid-infrared radiation. This system is based on a central quantum well (CQW) embedded in a superlattice. Because of the CQW, which acts as a defect, there are localized states between the mini-bands in the continuum of the conduction band. Unlike the usual systems where the final states are delocalized, the oscillator strength due to the transitions between electrons occupying the ground-state to these continuum-localized states is enhanced. An applied electrical bias mixes the mini-band states with the localized state in the continuum, and due to the combined effects of strong oscillator strength and high transmission coefficients, narrow and sharp peaks are observed in the photocurrent when exciting these final states. We calculate and present results of the absorption and photocurrent for a system built to operate at 4.1 µm and discuss their dependence with the bias applied to the system and with the intensity of the incident radiation.
A new approach to quantum well infrared photodetectors: Staircase-like quantum well and barriers
Infrared Physics & Technology, 2006
We present a theoretical investigation of a novel staircase-like quantum well infrared photodetector (QWIP). The proposed structure makes use of quantum wells and barriers with increasing Al content both in the wells and in the barriers forming a staircase-like energy band diagram without applied bias. The detection wavelength is around k = 12 lm at an applied electric field of F = 1.4 • 10 4 V/cm at room temperature. Device operation is based on inter-subband bound-to-bound transition. We have solved the energy band diagram of the structure self-consistently. We have also calculated the absorption coefficient, responsivity, total net quantum efficiency and dark current density at room temperature. The dark current density at the operating field was found to be around 10 À2 A/cm 2 , which is lower than the conventional QWIPs in the literature.
IEEE Sensors Journal, 2000
Recent commercial and military infrared sensors have demanded multispectral capabilities, high sensitivity and high selectivity, usually found in quantum well infrared photodetectors (QWIPs). This paper presents the design and characterization of a three-band QWIP capable to detect simultaneously near infrared (NIR), mid-wavelength infrared (MWIR), and long-wavelength infrared (LWIR), using interband and intersubband transitions. Separate readouts provide the flexibility to optimize each band detection by allowing the application of different bias voltages. The quantum well structure was designed using a computational tool developed to solve self-consistently the Schrödinger-Poisson equation with the help of the shooting method. The detector comprises of three different stacks of uncoupled (wide barriers) quantum wells that combine AlGaAs, GaAs, and InGaAs, separated by contact layers, grown by molecular beam epitaxy (MBE) on a GaAs substrate. The spectral responses in all three bands were measured using a standard photocurrent spectroscopy setup with light coupling via a 45 facet. The measured photoresponse showed peaks at 0.84, 5.0, and 8.5 m wavelengths with approximately 0.8, 0.03, and 0.12 A/W peak responsivities for NIR, MWIR, and LWIR bands, respectively. A good agreement between the measured and simulated figures of merit shows the possibility to improve and tailor the detector for several applications with low computational effort. Finally, this work has demonstrated the possibility of detection of widely separated wavelength bands using interband and intersubband transitions in quantum wells.
Progress in Symmetric and Asymmetric Superlattice Quantum Well Infrared Photodetectors
Annalen der Physik, 2019
Herein, two challenges are addressed, which quantum well infrared photodetectors (QWIPs), based on III-V semiconductors, face, namely: photodetection within the so-called "forbidden gap", between 1.7 and 2.5 microns, and room temperature operation using thermal sources. First, to reach this forbidden wavelength range, a QWIP which consists of a superlattice structure with a central quantum well (QW) with a different thickness is presented. The different QW in the symmetric structure, which plays the role of a defect in the otherwise periodic structure, gives rise to localized states in the continuum. The proposed InGaAs/InAlAs superlattice QWIP detects radiation around 2.1 microns, beyond the materials bandoffset. Additionally, the wavefunction parity anomaly is explored to increase the oscillator strength of the optical transitions involving higher order states. Second, with the purpose of achieving room temperature operation, an asymmetric InGaAs/InAlAs superlattice, in which the QW with a different thickness is not in the center, is used to detect infrared radiation around 4 microns at 300 K. This structure operates in the photovoltaic mode because it gives rise to states in the continuum which are localized in one direction and extended in the other, leading to a preferential direction for current flow.
Optical and Quantum Electronics, 2007
The subband energy dispersions and optical intersubband transitions in n-type InGaAs/Al x Ga 1−x As quantum well infrared photodetector (QWIP) with linear-graded barriers are calculated using an 8-band k·p model combined with the envelope-function Fourier expansion. The relaxation of quantum confinement in the growth direction has been taken into reasonable consideration. This work is helpful for the analysis and the design of QWIPs with complex well and barrier structures.
Quantum transport in quantum well infrared photodetectors in the tunneling regime
Infrared Physics & Technology, 2009
Quantum well infrared photodetectors (QWIP) are good candidates for low photon flux detection in the 12-20 lm range. For particularly low incident power applications, it can be interesting to reduce the operating temperature to reach the ultimate performance of the QWIP (low dark current, low noise, high detectivity). Nevertheless, once the QWIP operates in the tunneling regime, the dark current is no longer improved by reducing the temperature. Thus, further improvement of the performance needs a microscopic understanding of the physical phenomena involved in QWIP operation in the tunneling regime. In this paper we focus on the dark current of QWIP operated at very low temperature (4-20 K). Experimental results obtained on a 14.5 lm peaking device revealed a plateau regime in the IV curves. We first modeled the dark current using the WKB approximation, but it failed to reproduce the shape and order of magnitude of the phenomenon. As an improvement, we developed a scattering formalism. Our model includes all the most common interactions observed in GaAs: optical phonon, acoustical phonon, alloy disorder, interface roughness, interaction with ionized impurities and between carriers. We demonstrate that, as far as the tunneling regime is concerned, the dominant interaction is the one between electron and ionized impurities, which allows us to conclude on the influence of the doping profile on the dark current.