Niniejsza praca porusza zagadnienie charakteryzacji warstw epitaksjalnych arsenku indu (InAs) pod kątem jednorodności przestrzennej. Badania przeprowadzone w pracy zostały oparte na trzech metodach charakteryzacji: wysokorozdzielczej mikroskopii optycznej, mikroskopii sił atomowych i spektroskopii Ramana. Obiektem badań były warstwy epitaksjalne InAs na podłożach arsenku galu (GaAs), które zostały wytworzone metodą epitaksji z wiązek molekularnych (MBE).
EN
This thesis deals with the characterization of epitaxial layers of indium arsenide (InAs) in terms of spatial homogeneity. The research conducted in the paper was based on three characterization methods: high-resolution optical microscopy, atomic force microscopy and Raman spectroscopy. The subject of the research were epitaxial layers of InAs on gallium arsenide (GaAs) substrates, which were produced by the method of molecular beam epitaxy (MBE).
The paper presents noise measurements in low-resistance photodetectors using a crosscorrelation-based transimpedance amplifier. Such measurements usually apply a transimpedance amplifier design to provide a current fluctuation amplification. In the case of low-resistance sources, the measurement system causes additional relevant system noise which can be higher than noise generated in a tested detector. It mainly comes from the equivalent input voltage noise of the transimpedance amplifier. In this work, the unique circuit and a three-step procedure were used to reduce the floor noise, covering the measured infrared detector noise, mainly when operating with no-bias or low-bias voltage. The modified circuit and procedure to measure the noise of unbiased and biased detectors characterized by resistances much lower than 100 Ω were presented. Under low biases, the reference low-resistance resistors tested the measurement system operation and techniques. After the system verification, noise characteristics in low-resistance InAs and InAsSb infrared detectors were also measured.
We present an investigation of optical and electrical properties of mid-wavelength infrared (MWIR) detectors based on InAs/GaSb strained layer superlattices (SLs) with nBnN and pBnN design. The temperature-dependent behavior of the bandgap was investigated on the basis of absorption measurements. A 50% cut-off wavelength of around 4.5 μm at 80 K and increase of up to 5.6 μm at 290 K was found. Values of Varshni parameters, zero temperature bandgap E0 and empirical coefficients α and β were extracted. Arrhenius plots of dark currents of nBnN and pBnN detectors were compared with the p-i-n design. Dark current density reduction in nBnN and pBnN detectors is observed in comparison to the p-i-n device. This shows a suppression of Shockley-Read-Hall (SRH) processes by means of introducing barrier architecture.
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In this paper, we present experimental results of photoluminescence for series of InAs:Si heavily doped samples, with doping level varying from 1.6 × 1016 cm−3 to 2.93 × 1018 cm−3. All samples were grown using MBE system equipped with a valved arsenic cracker. The measurements were performed in the temperature range of 20 K to 100 K. Although the Mott transition in InAs appears for electron concentrations above 1014 cm−3, Burstein-Moss broadening of photoluminescence spectra presented in this article was observed only for samples with concentration higher than 2 × 1017 cm−3. For the samples with lower concentrations two peaks were observed, arising from the band gap and defect states. The intensity of the defect peak was found to be decreasing with increasing temperature as well as increasing concentration, up to the point of disappearance when the Burstein-Moss broadening was visible.
Opracowano warunki otrzymywania metodą Czochralskiego z hermetyzacją cieczową (Liquid Encapsulated Czochralski - LEC) bardzo czystych niedomieszkowanych monokryształów InAs typu n o ruchliwości elektronów μ > 22000 cm ² / Vs i koncentracji elektronów n < 3 x10^16 cm -³ w 300 K. Zbadano wpływ zawartości cząsteczek wody w topniku (B2O3) stosowanym do hermetyzacji stopionego wsadu na parametry elektryczne kryształów oraz na zawartość w nich domieszek resztkowych. Zbadano również wpływ czasu wygrzewania stopionego wsadu przed procesem krystalizacji na własności otrzymanych kryształów.
EN
The aim of this work was to find out technological conditions that allow obtaining high purity undoped InAs single crystals with carrier concentration below 3xl0^16 cm -³ and carrier mobility over 22000 cm ² / Vs. Synthesis by injection method and Liquid Encapsulated Czochralski (LEC) crystal growth were applied. The influence of water content in B2O3 encapsulant (applied during injection synthesis and LEC growth) on electrical properties of InAs crystals and especially on dopants concentration was investigated. The influence of charge annealing duration before crystallization process on InAs crystals properties was also investigated.
Fotodetektory z mikrownęką rezonansową są szczególnie przydatne w zastosowaniach, gdzie wymagana jest duża prędkość działania, jak np. we współczesnych systemach telekomunikacyjnych. W detektorach tych duża szybkość działania przy jednocześnie dużej sprawności kwantowej osiągnięta jest dzięki umieszczeniu obszaru aktywnego wewnątrz optycznej wnęki rezonansowej. W niniejszej pracy omówiony jest fotodetektor z mikrownęką rezonansową zaprojektowany na pasmo 1550 nm.
EN
Resonat cavity enhanced photo-detectors are promising candidates for application in high-speed optical communication and interconnections. In these photo-detectors both high bandwidth and high quantum efficiency can be achieved simultaneously due to standing wave formation in the resonant optical cavity. In this paper a state-of-the-art photo-detector designed for 1550 nm is presented.