Spectroscopic Research Of New Infrared Detection Materials And Devices Based On In, As, Ga, Sb

In this thesis, we investigate the far-infrared reflection spectra and photocurrentresponse spectra of InAsSb and InNSb films by using a fourier transform infraredspectroscopy (FTIR), we also investigate the time-resolved transient photovoltage ofInAs/GaSb type-II superlattice infrared detectors with p-b-i-n structure using apicosecond pulsed laser. And some achievements have been obtained from theresearch; the main points are listed as follows:(1) Two characteristic peak groups are detected in the reflection spectra ofInAsSb films by the FTIR. A multi-oscillator model with two phonons is used to fitthe results. The fitting results show that the frequency of the phonons changes as theAs fraction changes, and a Random-Element-Isodisplacement (REI) model can beused to explain the variation.By measuring the reflection spectra of the InAsSb films on the mismatched GaAssubstrate, it is found that there shows up a typical two-phonon vibration mode, goodfitting results can be achieved by using a Drude-Lorentz model. The fitting resultsshow that there is a shift of the phonon frequency compared with the theoreticalcalculation. By analyzing the regularity of the shift, one can conclude that it is thestrain caused by the mismatch between the epitaxy film and the substrate that leads tothis phenomenon. The carrier concentration and mobility can also be got by the fittingparameters of the plasmon, which is agreed with the theory. The carrier mobilitydecreases as the As fraction increases, which reflects that the lattice quality gets worsewhen the As fraction increases.(2) By using the black body and FTIR methods, the photoresponse of InAsSbdetectors at different temperatures and dimensions was measured. A wide-bandinfrared detector whose response peak at around4μm with4μm FWHM has beengot.Through the black body response testing, the responsivity and detectivity can be got. It is found that under the same testing bias, the black body responsivity decreasesas the dimension of the detector increases. And it is considered to be caused by thegain of the external quantum effieciency decreses as the dimension increases. Theresponse photocurrent spectra can be got by the FTIR. And there is a red shift of thecutoff wavelength copmpared with the theory. It is considered that because theInAsSb film is very thin, the large mismatch between the film and the GaAs substratewill cause CuPt-type ordering structure, which makes the energy gap decreases andcauses the red shift.(3) Using the far-infrared reflection spectra, black body testing and infraredphotocurrent spectra methods, unannealed and annealed InNSb films wereinvestigated at different temperatures. A prototype wide-band infrared detector whoseresponse peak at4.4μm and cut-off wavelength at5.7μm with the FWHM of3.5μmhas been obtained.At the investigation of InNSb films, through the reflection spectra, it is found thatthe damping of the InSb-like TO phonon in InNSb film is larger than that of the pureInSb film. It is because the N fraction breakes the long-range order structure of theInSb crystal. And it is found that the carrier concention is much larger than the pureInSb film, while the mobility is lower. It can be concluded that the introduction ofnitrogen makes many defects and abundant shallow energy levels in the materialwhich cause the carrier concentration very high and the mobility relatively low. Bytesting the photocurrent spectra, the cutoff wavelength shows a blue shift comparedwith the theory energy gap. It is the Moss-Burstein effect caused by the very highcarrier concentration makes this phenomenon. And the investigation proves that theannealing process can improve the lattice quality, decrease the carrier concentration,then suppress the Moss-Burstein effect, finally make the cutoff wavelength red shiftcompared with the unannealed situation.(4) The minority carrier lifetime can be got by investigating the time-resolvedtransient photovoltage of InAs/GaSb type-II superlattice infrared detectors withp-b-i-n structures. Measuring devices with different mesa areas, it is found that theapparent minority carrier lifetime increases as the area increases. Using a picosecond pulsed laser to make photoinjection, the minority carrierlifetime of InAs/GaSb type-II superlattice is investigated. By testing p-b-i-n structuredetectors with different mesa areas, the apparent minority carrier lifetimes are in the1~10ns order of magnitude. And the apparent lifetime trends to increase as the mesaarea increases. Because the side wall of the mesa can not be passivated very well,there exists surface assisted transport and surface recombination which will affect theapparent minority carrier lifetime.