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Chips with Everything
Published in Sharon Ann Holgate, Understanding Solid State Physics, 2021
Heterojunction lasers are diode lasers that can be made from two or more different semiconductors. They consist of a thin layer of semiconductor (for example, gallium arsenide), sandwiched between layers of a different semiconductor (such as aluminium gallium arsenide). They are made using epitaxial growth techniques (see Section 7.3.2). By contrast, as mentioned in the previous subsection, when a diode laser is made from just one semiconductor material, it is known as a homojunction laser.
mombe
Published in G B Stringfellow, Gallium Arsenide and Related Compounds 1991, 2020
G. E. Höfler, J. N. Baillargeon, J. L. Klatt, K. C. Hsieh, R. S. Averback, K. Y. Cheng
Heteroepitaxial Aluminium gallium arsenide (AlGaAs)/Indium gallium arsenide (InGaAs) structures which employ pseudomorphic modulation doped epitaxial layers grown on Gallium arsenide (GaAs) substrates provide major advantages for high speed, high frequency field effect transistor applications. Pseudomorphic modulation doped AlGaAs/InGaAs/AlGaAs with doping from both sides of the quantum well channel layer may fit this requirement. The authors have determined the scattering times of such pseudomorphic modulation-doped doped Al0.30Ga0.70 As/In0.17Ga0.83As structures grown by Molecular Beam Epitaxy either on an undoped GaAs buffer layer or on an undoped Al0.30Ga0.70As buffer layer. Appropriate interface grading and or increased substrate temperature during growth of the backside AlGaAs barrier, however, may improve interface quality and therefore the transport properties of these double barrier, modulation doped pseudomorphic heterostructures. The low field, oscillatory components of the magnetoresistance was extracted by digitally filtering the raw Shubnikov de Haasdata through a bandpass filter.
Detectors
Published in C. R. Kitchin, Astrophysical Techniques, 2020
Photoconductive detectors that do not require the electrons to be excited all the way to the conduction band have been made using alternating layers of gallium arsenide (GaAs) and indium gallium arsenide phosphide (InGaAsP) or aluminium gallium arsenide (AlGaAs), each layer being only ten or so atoms thick. The detectors are known as quantum well infrared photodetectors (QWIPs). The lower energy required to excite the electron gives the devices a wavelength sensitivity ranging from 1 to 12 μm. The sensitivity region is quite narrow and can be tuned by changing the proportions of the elements. Recently, the National Aeronautics and Space Administration (NASA) has produced a broadband 1k × 1k QWIP with sensitivity from 8 to 12 µm by combining more than a hundred different layers ranging from 10 to 700 atoms thick. Quantum dot infrared photodetectors (QDIPs) have recently been developed wherein the ‘well’ is replaced by a ‘dot’, i.e., a region that is confined in all spatial directions. It remains to be seen if QDIPs have any advantages for astronomy over QWIPs.
Intrasubband-related linear and nonlinear optical absorption in single, double and triple QW: the compositions, temperature and QW’s number effects
Published in Philosophical Magazine, 2023
Redouane En-nadir, Haddou El-ghazi, Walid Belaid, Mohammed Tihtih, Hassan Abboudi, Ibrahim Maouhoubi, Anouar Jorio, Izeddine Zorkani
During the last decade, group III-N semiconductor alloys including InN, GaN and AlN and their ternary alloys InGaN and AlGaN have been widely studied. They are beneficial materials for optoelectronic engineering and energy harvesting due to their particular optical and electrical properties. Their wide and direct band gap covers almost the entire electromagnetic spectrum from infrared (IR) to ultra-violet (UV) passing through the visible light. These properties make them potential candidates for various applications in the optoelectronic market dominated by conventional semiconductors including silicon (Si) and gallium-arsenide (GaAs) and aluminium-gallium-arsenide (AlGaAs) (e.g. blue and green LEDs, laser diodes, photodetectors, solar cells, all types of switches, etc.) [1–5]. InGaN-based heterostructures are one of the few systems capable of providing band gaps ranging from 0.7 (InN) to 3.4 eV (GaN) [6,7]. The adjustment of the forbidden band could be achieved directly by modifying the In-content in the InGaN alloys. InGaN-based systems can cover almost the entire visible spectrum. Therefore, InGaN alloys could be a perfect candidate for optoelectronic devices that operate under harsh temperature, voltage and pressure conditions [8,9]. Due to a direct band gap, the absorption coefficient of InGaN alloys is very high and reaches 105 cm−1 for a photon energy of 0.5 eV above the absorption edge for all ranges of in-compositions [10]. One of the challenging lockouts of Group III-N materials, especially the InGaN alloy, is that it is difficult to grow a thick layer of this later on GaN due to the high mismatch rate between them. The thick matrix layer of GaN is usually developed to match different materials by dislocation, bending and annihilation. Although the lattice mismatch between GaN and InN is lower (only 10%) compared to InN/sapphire and GaN/sapphire, it is still sufficient to cause stresses at the InGaN/GaN [11]. However, there is a critical thickness for InGaN layers above which stresses are released by forming dislocations. This critical thickness is much lower for InGaN grown on a GaN substrate and it is less than 5 nm for in-compositions greater than 20% [12]. Once the critical thickness is reached, thread dislocations form, damaging the performance of the device. One of the suggested ideas to avoid this problem is to grow thin layers of InGaN (InGaN-quantum wells) on GaN instead of a thick layer. This will certainly influence the performance of the device such as the optical absorption, which is the subject of this study. Quantum wells are a type of low-dimensional system (e.g. quantum dots and quantum wire wells) that allow us to confine carrier charges (electrons and holes) [13].