Normally the introduction of artificial resonate or filtering structures on the detection system, regardless of internally or externally, will increase the complexity, as well as cause losses, therefore a PD just matched to desired wavelength region inherently is strongly expected. Furthermore, a better performance of the detector could be expected for a material with larger bandgap, regardless of some other effects. Normally, it will not cutoff sharply but drop continuously until reaching an unacceptable level. The response of the detector at short wavelength side is depending on the material properties, device structures and so on. For a quantum type PD operating in certain wavelength region, regardless of artificial resonate or filtering structures, the cutoff wavelength at long wavelength side is determined by the bandgap of the sensitive material inherently.
Cd cut off wavelength full#
However, outside the anticipant sensitive wavelength region a full cutoff of the PD is preferable, because in this case the response is not a signal but noise or interference to the applications. Normally, inside the anticipant sensitive wavelength region a high response of the detector is expected. The expected sensitive wavelength region of a PD is mainly depending on its application requirements. The materials for quantum type PDs sensitive to UV-visible bands could be chosen from group IV (e.g.: Si, SiC), group III-V (nitride, phosphide or arsenide), group II-VI (e.g.: CdS, CdTe) and so on, mainly depending on their bandgap (e.g. In UV-visible bands normally quantum or photon type PDs, instead of thermal type PDs, are preferable. Finally, the performance of developed AlInP-GaInP-GaAs and AlInP-GaAs photodiodes tailored for specific wavelength range will be characterized and discussed.Ģ.1. The doping, structural and optical properties of the GSMBE grown materials will be investigated in detail, then turning into the growth of PD structures and processing of the device chips composing of those ternaries, mainly based on our experience. In this chapter, a simple review on the material issues of PDs in these bands will appear first, then concentrated on the gas source molecular beam epitaxy (GSMBE) growth of the ternaries lattice matched to GaAs substrates, including GaInP and less-studied AlInP. Furthermore, for this GaAs based III-V non-nitride system, the doping in both n and p type is feasible, a quite mature growth and processing technology can be relied on, so photovoltaic detectors and arrays with better performance could be presumed. Besides, profiting from the wider bandgap comparing to that of Si, higher working temperature, lower dark current and better radiation hardness could be expected for those robust materials.
Al 0.52In 0.48P and Ga 0.51In 0.49P, which are lattice matched to GaAs substrate, have band gaps about 2.3 eV and 1.9 eV respectively, the combination of those two ternary materials, in conjunction with the quaternary AlGaInP system, also gives a big room in tailoring the response of the photodiodes to a specific wavelength region. Among various optional materials in those bands, the III-V Al(Ga)InP system, especially the ternary AlInP and GaInP, may work well in visible or even extending to UV band. Among them, Si PD should be the most successful one, whereas its wide response extends to near-infrared inherently, also, the performance of Si PD is limited by its indirect and relatively narrow bandgap, which restricts its applications in certain cases. In those wavelength bands, various groups of II-VI, III-V and VI materials could be utilized for PDs. Photodiodes or photodetectors (PDs) with specific wavelength response in UV-visible bands have many practical and potential applications including ocean or water related sensing and communication, medical engineering and photodosimetry, missile guidance and countermeasures, and so on. Therefore, the spectral response features of life-forms including human beings, as well as plentiful artificial creatures, are linked to those bands spontaneously and tightly. The sun light shining on our earth, with its main energy concentrated in visible extending to ultraviolet (UV), has activated this planet adequately.
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