Improvement of electrical properties of ZnS/CdTe-HgCdTe interface by (NH4)2S treatment
TL;DR: In this article, the effect of 20% aqueous ammonium sulphide treatment on electrical properties of ZnS/CdTe-HgCdte interface was studied by using high frequency capacitance-voltage (C-V) measurements showing significant improvement in surface conditions.
About: This article is published in Infrared Physics & Technology.The article was published on 2019-11-01. It has received 8 citations till now.
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TL;DR: In this paper, the capacitance and voltage characteristics of metal-insulator-semiconductor (MIS) structures based on HgCdTe with traditional CdTe/ZnS and ULT-ALD ZnS passivation are studied.
3 citations
TL;DR: In this article, the long-term passivation of GaAs surfaces induced by the use of a saturated ammonium sulfide solution under optimum condition was investigated and the X-ray photoelectron spectroscopy (XPS) study was conducted to prove the results.
Abstract: The application of III–V semiconductors, including GaAs, in various optoelectronic devices has attracted considerable attention due to their high electron mobility. The presence of native oxide on GaAs surfaces causes a high surface density of states that can be removed by passivation techniques. One of the most common passivation approaches is the ammonium sulfide ((NH4)2Sx) treatment; however, the GaAs surface tends to re-oxidize after passivation in a short time. This study presents the long-term passivation of GaAs surfaces induced by the use of a saturated ammonium sulfide solution under optimum condition. The X-ray photoelectron spectroscopy (XPS) study was conducted to prove our aim. XPS results demonstrate the removal of the native oxide layer from the GaAs surface immediately after passivation and the absence of surface re-oxidation for several days after passivation and air exposure. Therefore this approach can be used as an effective way to achieve stable passivated surface of GaAs.
3 citations
TL;DR: In this article, an enhancement of gas sensing characteristics of GaAs-based Schottky diode sensors passivated by ammonium sulfide is studied and demonstrated, showing a response of 63% upon exposure to 600ppm ammonia gas at a working temperature of 150°C, which is about 2.5 times higher than that of the non-passivated sensor.
Abstract: In this work, enhancement of gas sensing characteristics of GaAs-based Schottky diode sensors passivated by ammonium sulfide are studied and demonstrated. The GaAs surface is passivated by saturated ammonium sulfide solution to remove its native oxide and reduction of surface state densities. The measurements indicate a significant improvement in electrical characteristics of Pt-Pd(alloy)/GaAs diode where the Schottky barrier height increases from 0.688 to 0.758eV after surface passivation. The Schottky diode with passivated GaAs surface exhibits a response of 63% upon exposure to 600ppm ammonia gas at a working temperature of 150°C, which is about 2.5 times higher than that of the non-passivated sensor. This noteworthy improvement is attributed to the decrement of metal-semiconductor interface states, preventing the Fermi level pinning. Furthermore, the response (recovery) times of 29 (138)s is obtained upon exposure to 600ppm ammonia at 150°C, showing a value of around 2 times lower than that for the non-passivated sensor.
2 citations
Cites methods from "Improvement of electrical propertie..."
...Surface passivation using ammonium sulfide solution is one of the best methods to eliminate the native oxide on the GaAs surface, decreasing the surface density of state and thus enhancement of electrical characteristics of GaAs based diodes [21], [27]–[29]....
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05 Nov 2020
TL;DR: In this article, a new method was proposed to remove the self-generating oxide layer and residual rich tellurium layer to obtain a good in function HgCdTe infrared detector.
Abstract: HgCdTe is significant material prepared infrared detector. Higher performance infrared detector and longer wavelength are vital requirements of the third infrared detector. Device performances of HgCdTe infrared detector and material interface state are inseparable. On the one hand, the HgCdTe lattice is zinc-blende cubic structure, when it is exposed to atmosphere, self-generating oxide layer can be forming on material interface, a good deal of fixed charges are existing in the oxide layer, that can make the device properties degradation seriously. On the other, in the traditional preparation process, epitaxial HgCdTe layer is corroded before surface passivation, material surface could form residual rich tellurium layer. It can also make the device properties degradation on account of recombination centers, increase surface leakage of the device. Based on the above, study on the surface treatment process of HgCdTe detector is very necessary, this paper researched a new method wiping out the self-generating oxide layer and residual rich tellurium layer to obtain a good in function HgCdTe infrared detector. In this way, prepared HgCdTe infrared detector containing cutoff wavelength of 5 μm, 9μm and 12.5 μm, compared HgCdTe infrared detector employing this new method and unused this new method. The former possessed lower dark current, lower noise equivalent temperature difference (NETD) and higher yield. This new method applying to process of HgCdTe infrared detector enhanced the detector properties, lay the foundation of longer wavelength HgCdTe infrared detector.
1 citations
TL;DR: In this article , an aligned nanofibers were prepared by electrospinning process, and the performance of aligned In
Abstract: Indium oxide (In $_{\text{2}}$ O $_{\text{3}}\text{)}$ is a metal–oxide–semiconductor material with excellent performance. Due to its very large carrier mobility, it is considered a suitable choice for the fabrication of field-effect transistors (FETs). In this report, aligned nanofibers were prepared by electrospinning process, and the performance of In $_{\text{2}}$ O $_{\text{3}}$ nanofiber FET was adjusted by controlling the electrospinning time. The results show that the FET based on aligned In $_{\text{2}}$ O $_{\text{3}}$ nanofibers exhibits excellent electrical properties at an electrospinning time of 2 min, including the mobility ( $\mu$ FE) of 11.52 cm $^{\text{2}}$ /Vs, switching current ratio ( $\textit{I}_{\text{on}}$ / $\textit{I}_{\text{off}}\text{)}$ of 2.5 $\times$ 10 $^7$ , and subthreshold swing (SS) of 0.36 V/dec, and it shows good stability under positive bias stress (PBS). This method of preparing aligned metal–oxide nanofibers by electrospinning to achieve FET with high performance, low power consumption, and high stability is very suitable.
References
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TL;DR: In this article, the M-O-S diode was introduced, and a theory for its operation in the absence of surface states was obtained, and it was shown that surface states with non-zero relaxation times may increase the capacitance of the device, as well as affect the proportion of applied voltage which appears across the silicon.
Abstract: A new solid-state device, the M-O-S diode, of which an oxidized silicon surface is an integral part, is introduced, and a theory for its operation in the absence of surface states is obtained. The capacitance of this device may be considerably more voltage sensitive than that of a p-n junction. The existence of surface states with non-zero relaxation times is introduced into the theoretical model. It is shown that the states may increase the capacitance of the device, as well as affect the proportion of applied voltage which appears across the silicon. A small-signal equivalent circuit is derived which includes the effect of the surface states. It is also shown that a comparison of the theoretical capacitance vs. voltage curve without states and a measured high-frequency capacitance vs. voltage curve may be used to obtain the distribution of all states, regardless of their time constants. Results are given of measurements and calculations on two M-O-S diodes having different surface treatments before oxidation. Both surfaces have a total density of about 3 × 10 12 states/cm 2 . In both cases, the distribution of states is continuous and has its highest peak about 100 mV above E F (0), the position of the Fermi level at the silicon surface if there is no voltage drop across the silicon The time constants of the states extend from 10 −8 sec to longer than 10 −2 sec. There is a tendency for states located at deeper energy levels to have longer time constants, but some of the states in the high density of states above E F (0) have long time constants. The distribution of time constants with energy level is somewhat different for the two surfaces. A comparison is made between the distribution of states obtained here with the distribution reported by others working in the field. The results are similar in density and location of the peaks of the distribution reported here, but differ in that some other sources report a discrete distribution.
1,331 citations
Abstract: This article presents a review on the current status, challenges, and potential future development opportunities for HgCdTe infrared materials and detectortechnology. A brief history of HgCdTe infrared technology is firstly summarized and discussed, leading to the conclusion that HgCdTe-based infrared detectors will continue to be a core infrared technology with expanded capabilities in the future due to a unique combination of its favourable properties. Recent progress and the current status of HgCdTe infrared technology are reviewed, including material growth,device architecture, device processing, surface passivation, and focal plane array applications. The further development of infrared applications requires that future infrared detectors have the features of lower cost, smaller pixel size, larger array format size, higher operating temperature, and multi-band detection, which presents a number of serious challenges to current HgCdTe-based infrared technology. The primary challenges include well controlled p-type doping, lower cost, larger array format size, higher operating temperature, multi-band detection, and advanced plasma dry etching. Various new concepts and technologies are proposed and discussed that have the potential to overcome the existing primary challenges that are inhibiting the development of next generation HgCdTeinfrared detectortechnology.
235 citations
TL;DR: In this article, a model is presented to explain why and how the GaAs surface is passivated and stabilized by (NH4)2Sx treatment and the model successfully interprets different experimental data on the surfaces treated with solutions of sodium sulfide and ammonium sulfide with and without excess sulfur.
Abstract: A model is presented to explain why and how the GaAs surface is passivated and stabilized by (NH4)2Sx treatment. Natural oxide, together with a thin layer of GaAs, is removed and the fresh GaAs surface is covered with a monoatomic layer of sulfur which has no dangling bonds. On this surface, foreign atoms are prohibited from chemical adsorption. Thus, the As and Ga vacancies which are, according to Spicer's "unified defect model", the cause of the interface trap level are not introduced. The present model of the passivation successfully interprets different experimental data on the surfaces treated with solutions of sodium sulfide and ammonium sulfide with and without excess sulfur.
168 citations
TL;DR: The practical aspects of HgCdTe surface passivation, as related to devices and applications, are reviewed in this article, where a two-layer combination of a thin native film with a thick deposited dielectric film is presented.
Abstract: The practical aspects of HgCdTe surface passivation, as related to devices and applications, are reviewed. Currently used technologies are classified in two categories: thick deposited dielectrics and a two‐layer combination of a thin native film with a thick deposited dielectric film. The first category includes ZnS, low‐temperature photochemical vapor deposited SiO2 (photox), and electron cyclotron resonance plasma deposited SiNx. The second category includes anodic oxide, plasma oxide, photochemical native oxide, anodic sulfide, and anodic fluorides. The unique behavior of HgCdTe surfaces, metal‐insulator semicoductor structures, and gate‐controlled p–n junctions are reviewed. The surface requirements of HgCdTe devices of interest for present and next‐generation focal plane arrays are discussed in terms of the reviewed technologies.
130 citations
TL;DR: In this paper, the effects of an (NH4)2S surface treatment on the formation of Schottky barriers on n and p-type GaAs were investigated and it was shown that the surface state density of GaAs is increased by a reduced pinning of the Fermi level at the surface.
Abstract: Because of a large surface state density, which effectively pins the Fermi level at the surface, metals with vastly different work functions and chemistry produce very similar Schottky barriers when deposited on GaAs. We have investigated the effects of an (NH4)2S surface treatment on the formation of Schottky barriers on n‐ and p‐type GaAs. Samples which have undergone the (NH4)2S treatment show a reduced pinning of the Fermi level at the surface and hence Schottky barriers which are more sensitive to the metal work function.
118 citations