The InAs/GaSb superlattice infrared detectors have attracted more and more attention due to they have the properties of adjustable energy band, high uniformity, low Auger recombination, tunneling current, and high quantum efficiency. At present, it is widely used in the preparation of long-wave infrared detectors. This paper studies the effects of different passivation methods on device performance. The dark current density of the device which uses silicon nitride film as the passivation layer can be reduced to 5.01×10-5A/cm2 , and its maximum impedance can reach 421 Ω·cm2 , then we used energy band theory to explain the reason for this phenomenon. We believe that the occurrence of this phenomenon is related to the wider band gap of nitride, because the wider forbidden band can suppress the generation of surface leakage current, thereby reducing the dark current density and improving the performance of the device.
In the research of the InAs/GaSb type II superlattice, MW/SW、MW/LW、MW/MW two color superlattice infrared focal detector has been developed abroad [1]. In this paper, we study the uniformity, compactness and etching resisrance of the mask prepared by PECVD. It has been proved that dry etching can satisfied the superlattice material etching depth by experiment [2]. When the experimental condition is that the CH4:H2:Cl2:Ar flow ratio is 8:15:6:15, ICP power is 400 W, and the reaction pressure is 1.0 Pa,it can be etched to the requirements of two-color superlattice depth with clear、flat mesa and no residual generation [3]. The experiment optimizes the etching technology of two-color superlattice material, and the etching result meets the requirements of the etching depth and quality of the two-color superlattice chip.
The InSb epitaxial layer of p+-n-n+ structure was grown by Molecular Beam Epitaxy (MBE) on a heavily doped InSb substrate. Photodiodes of InSb were fabricated by standard semiconductor manufacturing process. Measurement and analysis of its electrical properties was carried out. Compared with traditional bulk crystal InSb of p+-n structure, we find that, when the external bias voltage is 0.1V, dark current density values of p+-n-n+ InSb device and InSb bulk material device is 1.1×10-6 A·cm-2 and 9.5×10-5 A·cm-2 at 77K, respectively. zero-bias-resistance area products is 8.9×104Ω·cm2 and 6.2×103 Ω·cm2 at 77K, respectively. Doping concentrations values in the absorption layers are equal to 5.0×1014 cm-3 and 1.3×1016 cm-3 , respectively. The InSb epitaxial layer of p+-n-n+ structure which has better crystal quality achieves better performance than bulk crystal InSb when the passivation process is reliable. It provides an important foundation for the fabrication of epitaxial InSb infrared detector.
Infrared(IR)photo detectors based on InAs/GaSb type II superlattice have developed quickly in recent years. Many groups show great interest in InAs/GaSb superlattice detector for its superiors as high quantum efficient, high working temperature, high uniformity and low dark current densities. Inductively coupled plasma(ICP) etching of GaSb and InAs/ GaSb superlattices were performed using Cl2/Ar/CH4/H2. This paper introduceste inductively coupled plasma( ICP) etching of Inas/GaSb with SiO2 mask by the Cl2/Ar/CH4/H2 mixed-gas process. The effects of process parameters such as gas combination, ICP and RF power on the etch rate and quality of InAs/GaSb It is found that the ratio of Cl2 flow rate significantly affects the etch rate, due to the trade-off between physical and chemical component of etching. The etch rate of InAs/GaSb increases with the increase of percent of Cl2, there will InClx remains in the etching channel when the etching depth exceeded 2μm, which can stop the etching going on. This phenomenon can be eliminated by decrease the Cl2 ratio,to make sure the etching depth reach 6μm under a certain low etching rate. The surface morphology and SEM of the superlattice material after etching shows that dry etching morphology is better than wet etching.After the electrode is grown, the superlattice chip have a good diode characteristic curve.
Indium tin oxide (ITO) films were deposited on sapphire substrates at temperatures ranging from 30°C to 700°C and oxygen background pressure changing from 0.05 Pa to 0.25 Pa by femtosecond pulsed laser deposition (PLD). The films were characterized using metallurgical microscope, film resistance meter and Fourier transform infrared spectrometer to study the effect of substrate temperature and oxygen background pressure on the surface topography, sheet resistance and infrared transmission. The photographs of metallurgical microscope show that substrate temperature plays a dominant role on the surface morphology of the films. The sheet resistance test suggests that the sheet resistance of the film decreases with increase of substrate temperature but increases with increase of oxygen background pressure. The results of infrared transmission show that the infrared transmission through the ITO film is about 40% at the wavelength of 1.5μm to 1.8μm and is very low at other infrared band. The films deposited at higher substrate temperatures show lower value of transmittance, and which at higher oxygen background pressure show higher value of transmittance.
Type II InAs/GaSb superlattice material, because of its excellent predominance, is becoming the best choice for the third generation infrared detector. Surface passivation, which is one of the most important process during the device fabricated, can improve the performance of superlattice detector greatly. In this work, three passivation methods were experimented based on MWIR superlattices, then after electrodes were fabricated, detectors were tested. From the measurements, the passivation of anodic sulfide cooperating with SiO2 is more effective than others, zero-bias resistance area product of device with 5μm cutoff wavelength reach up to 104Ω•cm2 at 77K, reverse-bias dark current density is reduced to 10-5A/cm2 at -1V, peak detectivity is 1010cm•Hz1/2/W and quantum efficiency reach 35%. Retest after a month later, the performance of photodiodes without diversity.
A series of InSb thin films were fabricated on the sapphire substrate by femtosecond pulsed laser deposition (fsPLD)
method with the laser of 110 fs pulse width. The laser incident energy is near 1mJ. The target is one kind of heavily
doped n-type InSb. The substrate temperature changes from 80 ºC to 400 ºC, Laser frequency changes from 1 Hz to 1 kHz and laser energy density changes from 0.1 J/cm2 to 1 J/cm2. The effects of different laser frequencies, substrate temperature and laser energy density on the surface morphology and optical property have been investigated separately. The surface morphology of InSb thin films was observed by metallurgical microscope and scanning electron microscope (SEM). The thin film with better surface morphology is obtained when the laser frequency is 10 Hz, substrate temperature is 80 ºC and laser energy density is 0.1 J/cm2. X-ray diffraction (XRD) demonstrates that the InSb thin film has a good single crystal structure. The infrared transmittance of InSb thin films is measured by an infrared spectrometer. The results show that good InSb thin films can be prepared by fsPLD. It is found that the mid-wavelength Infrared transmission through the InSb thin films is near 55% and it almost does not change under the different growing conditions.
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