Characterization of deep levels in high electron mobility transistor by conductance deep level transient spectroscopy

The influence of a substrate voltage on the dc characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) on silicon (111) substrate is profited to investigate traps that are located between the substrate and the two-dimensional electron gas (2DEG) channel. The transient of the drain current after applying a negative substrate voltage is evaluated in the temperature range from 77 to 600 K. With this method, known as Conductance Deep Level Transient Spectroscopy (CDLTS), majority deep levels with activation energy of 61 meV as well as minority carrier traps at 74 meV and capture cross-section respectively 2.56 × 10^− 15 cm², 2.1 × 10^− 15 cm² are identified. Finally, the correlation between the anomalies observed on the output characteristics and defects is discussed.     

A study of side gate test structures in InAlAs/InGaAs HEMTs for optoelectronic circuit applications

The InAlAs/InGaAs HEMT is a key electron device used in optoelectronic integrated circuits (OEICs) operating in the 1·3 and 1·5 μm optical wavelength ranges. OEIC performances can be degraded by side-gating effects associated with the HEMT. A side gate current is evidenced and demonstrated to be (i) due to a hole current induced by an impact ionization mechanism into the HEMT InGaAs channel and flowing through the InAlAs buffer layer and (ii) strongly dependent on the side gate test structure geometries and types of contacts. Finally, an optimized structure for monolithic integration is presented together with requirements on the operating point.     

基于InP衬底的应变和应变补偿的InGaAs／InAlAs材料的高分辨X射线衍射分析

高分辨率X射线衍射技术被用来分析基于InP衬底的应变的InGaAs和InAlAs单层材料和应变补偿的InGaAs/InAlAs超晶格材料.通过倒空间mapping得到的单层材料的错向角大约为10-3度,可以忽略不计.通过摇摆曲线得到了单层材料的组分和体失配度,接着单层材料的结果被用来分析在相同的条件下利用MBE技术生长的超晶格材料.利用倒空间mapping精确得到了超晶格的平均垂直失配度和各层的厚度,通过X射线模拟软件得到的超晶格材料的模拟曲线和实测曲线吻合的很好.     

Low frequency noise analysis to detect the influence of deep levels in AlGaAs/GaAs st

Low frequency noise measurements have been performed on conventional AlGaAs/GaAs HEMTs in the temperature range 110-300K and in the frequency range 10 Hz-25kHz. The characteristics of deep levels have been determined from the channel noise current spectral intensity evolution versus the temperature. The contribution of the DX centre to the channel noise current has been evaluated for different gate bias. A correlation between the parasitic MESFET operation in the HEMT and the channel noise behaviour has been found.     

Zero-Magnetic-Field Spin Splitting of Conduction Subbands in InGaAs/InAlAs and GaAs/AlGaAs Quantum Wells

Zero-magnetic-field spin splitting in InGaAs/GaAs and GaAs/AlGaAs multiple quantum wells was investigated theoretically. The sp³s* empirical tight-binding method has been employed. It has been found that the splitting is much larger in InGaAs wells than that in GaAs wells. The origin of the splitting due to the structure inversion asymmetry was briefly discussed.     

Capacitance–voltage profile characteristics of Schottky barrier structure with InAs quantum dots grown on InAlAs/InP(001)

Capacitance–voltage, C(V) studies have been carried out on Schottky barrier structure containing a sheet of self-organized InAs quantum dots (QDs) grown on InAlAs lattice matched to InP in order to deduce the electrical properties of the QDs. Three electron levels have been detected in n-type material, and were attributed to the s ground, the p excited, and the d excited states. Some parameters of the structure, such as the position of the InAs QD plane, the electron concentration in the QDs and an approximate QD height were deduced from the C(V) profile analysis. These results are in good agreement with the transmission electron microscopy (TEM) study realized on the structure.     

Influence of LPE growth conditions on the electroluminescence properties of InP/InGaAs(P) infrared emitting diodes

Liquid phase epitaxial growth of InP/InGaAs(P) infrared emitting diodes was studied systematically. Small area surface emitting LED chips were prepared to cover completely the 1100–1700 nm wavelength ranges. Nine different diodes were fabricated with optimal spacing of the peak emission wavelengths in order to have sufficient overlapping of their spectra. Efficient LEDs with narrow spectra have been realised by careful selection of the layer structure and growth conditions. Thick active layers with constant composition and abrupt interfaces have been grown for each emission wavelength. The long wavelength diodes (1275–1675 nm) were grown with additional quaternary layer(s) to prevent the melt-back of the active layer by InP melt. Low growth temperature (590°C) was used to prepare the LED structures. In the spectral range of 1250–1520 nm higher growth temperatures (625–645°C) were necessary to improve the device parameters. Such phenomena confirm the existence of the miscibility gap in the InGaAsP quaternary crystal system. Quaternary layers grown in the middle of the immiscibile region showed non-uniform composition and ragged interfaces at the upper heterojunction.     

Magnetism and Magnetocaloric Properties of Mn3Zn1-xSnxC and Mn3-xCrxZnC Compounds

Upon substitution of Sn for Zn,the Curie temperature of Mn 3 ZnC is lowered from 380 to 375 K for Mn 3 Zn 0.95 Sn 0.05 C and to 305 K for Mn 3 Zn 0.75 Sn 0.25 C.In accordance with the second-order ferromagneticparamagnetic transition,a room-temperature magnetocaloric effect without thermal and magnetic hysteresis is observed over a wide temperature range.The maximum value of the magnetic-entropy change S M for a magnetic-field change from 0 to 5 T is 2.42 J.kg 1.K 1 at 386 K for Mn 3 Zn 0.95 Sn 0.05 C and 1.70 J.kg 1.K 1 at 308 K for Mn 3 Zn 0.75 Sn 0.25 C.Meanwhile,substitution of Cr for Mn lowers the temperature of ferromagneticferrimagnetic transition from 233 K for Mn 3 ZnC to 230 K for Mn 2.9 Cr 0.1 ZnC and to 175 K for Mn 2.1 Cr 0.9 ZnC.An inverse magnetocaloric effect with S M equal to 0.28 J.kg 1.K 1 at 223 K for a field change from 0 to 1.47 T is observed for Mn 2.9 Cr 0.1 ZnC.     

Crystallographic dependence of OMVPE InGaAs/InP lateral growth on patterned (100) InP substrates prepared by wet etching

InP layers and InP/InGaAs structures were grown at 600°C using OMVPE on non-planar wet-etch InP substrates with patterns aligned at various angles Θ within [010] and [01-1] as well as [001] and [0-11]. The patterns were 15-μm-high ordinary mesa-shaped ridges with the sidewall facet angle dependent on the alignment angle Θ. Within 0.5°<Θ<10°, the morphology of InP exhibited ledges running down the slope of the facet, which increased the surface roughness. For larger angles Θ, it exhibited different features. The nucleation of InGaAs proceeded through faceted trapezoidal features. This type of nucleation was not suppressed on the facets for 0.5°<Θ<10°. For larger Θ, the InGaAs morphology exhibited different features.     

Influence of interface compounds on interface bonding characteristics of aluminium and silicon carbide

The interface plays an important role in improving the mechanical properties of metal matrix composites. Hence, it is essential to evaluate interface bonding of Aluminium/Silicon carbide. The interface bonding of Aluminum/Silicon carbide samples were prepared by various processing temperatures at constant holding time. The interface compounds at the interface were evaluated by an energy dispersive spectroscope and diffusion length of compounds was calculated by Arrhenius equation. The interface structure was analyzed by a scanning electron microscope. The interface characteristics were evaluated by tensile test and microhardness test.     

Temperature dependent study on the microwave noise performance of metamorphic InP/InGaAs heterojunction bipolar transistors

In this study, a detailed characterization on the microwave noise performance of high gain metamorphic heterojunction bipolar transistor (MHBT) in the temperature range of 300 K to 380 K is performed. The results are compared between the MHBT and the referenced lattice-matched InP HBT (LHBT) devices. The minimum noise figure (NF_min) versus frequency in the range of 2 to 20 GHz at different temperatures for a 1.6 × 20 μm² HBTs are measured. The experimental results show that the MHBT exhibits a slightly larger variation in NF_min compared to lattice-matched HBTs. Even though the MHBTs may have much higher thermal resistance, this may not significantly affect the device microwave noise performance.     

Optimization of growth of InGaAs/InP quantum wells using photoluminescence and secondary ion mass spectrometry

InGaAs/InP quantum wells of widths varying from 19 Å to 150 Å have been grown by MOVPE and the growth temperature optimized using photoluminescence and SIMS. It was thus found that for a 78 Å well the lowest PL linewidth of 12.7 meV at 12 K was obtained for growth at 625°C. SIMS also showed sharpest interfaces for this temperature compared with growth at 610°C and 640°C. The well widths determined from PL energies were in good agreement with a growth rate of 8.25 Å/s. However, while the barrier widths of 150 Å were in agreement with SIMS results, the well widths from SIMS were found to be much larger, due to a lower sputtering rate of InGaAs compared with InP. Quantitative comparison was made assuming the presence of InAsP and InGaAsP interface layers on either side of the wells and the relative sputtering rates determined.     

Influence of heating of the active region in InGaAsP/InP injection lasers on their spectral characteristics

Spectral and spatial characteristics of the output of InGaAsP/InP separate-confinement double heterostructure laser are investigated. The measurements are performed in quasicontinuous and continuous pumping regimes at room temperature. These lasers are shown to be spatially single-mode over the entire working range of currents. The broadening of the longitudinal modes under quasicontinuous pumping is attributed to heating of the active region of the lasers. The pump pulse duration at which heating of the active region of the lasers can be neglected is estimated. Pis’ma Zh. Tekh. Fiz. 25, 88–94 (April 26, 1999)     

Study of photoluminescence and computation of configuration coordinate diagram of Cu related deep levels in InP

Photoluminescence has been studied in Cu diffusedn andp-InP. Inp-InP a Cu related photoluminescence (PL) band was observed at 1·216eV. The temperature dependence of line-width was studied and line-shape and line-width analysis carried out. The configuration coordinate diagram of the band was calculated which showed a small lattice relaxation of 0·079 Å. Inn-InP two PL bands at 1·20 and 1·01 eV were found at 10 K. The former was similar to the 1·216eV band inp-InP. The PL of the 1·01 eV band was also studied in detail and the corresponding configuration coordinate diagram derived.     

Analysis of the relationship between the kink effect and the indium levels in MOS transistors

In this work, we investigate the effects of indium ion implantation on the channel of nMOSFETs. Deep level transient spectroscopy (DLTS) and admittance spectroscopy (AS) measurements have been made on a series of indium doped silicon N⁺P structures and MOS capacitors. To analyse the indium-related levels in nMOSFETs, we used a low frequency (LF) output conductance dispersion analysis, which is based on the Gain-Phase versus frequency at different temperatures. These experiences show that the indium level when operated at low temperatures at which the majority of carriers freeze-out exhibit a kink effect. The effects of indium doping on the kink were studied using the variation of channel conductance g_d and transconductance g_m versus temperature in the kink zone. The excess drain current versus drain and gate voltage show the maximums of both conductance g_d and transconductance g_m at around T = 124 K when the indium level is activated.     

Influence of the position of InGaAs quantum dot array on the spectral characteristics of AlGaAs/GaAs photovoltaic converters

Results of a comparative study of the internal quantum yield of AlGaAs/GaAs photovoltaic converters (PVCs) with variable position of the array of vertically coupled InGaAs quantum dots (QDs) are presented. It is established that the QD array placed immediately at the i-region/base interface does not change the PVC sensitivity compared to that for QDs arranged inside the i-region of the p-n junction. However, the QD array shifted to the base or the back potential barrier decreases the contribution of a base layer to the PVC photocurrent and reduces the photosensitivity of the QD-based medium.     

The effect of Cr barrier on interfacial reaction of Au/Zn/Au/Cr/Au contacts to p-type InGaAs/InP

Alloy-type metal is widely used to reduce contact resistance in optoelectronic devices. Among the alloy-types, Au/Zn is one of the most common metallization systems. In this paper, we studied the alloy morphology of p-InP/p-InGaAs/Au/Zn/Au/Cr/Au systems. We found that the amount of Au-Zn alloy depended upon the thickness of the Cr layer. When Cr thickness was reduced to 135 Å, both Au-rich and GaAs-rich excessive compound formation started to occur. The Au diffusion punched through the InGaAs layer and penetrated into the InP. Comparison of Au/Zn/Au and Au/Zn/Au/Cr/Au suggested that the top Au layer maybe very influential during the alloy reaction. The Au-Zn alloy was significantly less in the Au/Zn/Au than that in the Au/Zn/Au/Cr/Au.     

Observation of thermal effects due to an optical incident signal and high fluence on InGaAs/InP multiple-quantum-well saturable absorber nonlinear mirrors: evolution of characteristics and time constants

We observe the effects of a temperature increase on the characteristics of an InGaAs/InP multiple-quantum-well (MQW) saturable absorber (SA) in a microcavity provided by an optical input signal under normal incidence. The temperature increase on the nonlinear mirror (NLM) due to an optical signal depends on the energy time filling factor (FF) of this input signal (analogous to the signal's duty cycle, which is the ratio between the repetition period and the pulse duration) and hence depends on the repetition rate of the signal for a given pulse time width. This increase in temperature is mostly responsible for a shift in the reflectivity spectrum of the device toward higher wavelengths. In this experimental study, we show the shift of the resonance cavity versus the optical input power at high FF, and we evaluate the thermal time constant of an Fe-doped InGaAs/InP MQW NLM. Finally, we report the consequences of such thermal effects and high fluence on the reflectivity and contrast of two different InGaAs/InP NLMs when the input signal FF rises up to 25%, which gets close to telecommunication transmission conditions.     

Influence of illumination on the output characteristics in pentacene thin film transistors

The influence of illumination on the output characteristics of pentacene-based organic thin film transistors (OTFTs) was researched in this study. It is shown that light illumination may lead to an increase in the drain current, shifting the threshold voltage towards positive gate–source voltages. This is because of the light-induced acceptor activation, which is a new concept for illumination-dependent output characteristics of OTFTs. However, the field-effect mobility is insensitive to light illumination. It is found that electron trapping is responsible for the experimentally observed illumination-dependent output behavior of charge transport in OTFTs.     

Influence of gate thermal oxide layer on InGaP/InGaAs doping-channel field-effect transistors

In this article, the significant effect of a thin gate thermal oxide layer on InGaP/InGaAs doping-channel field-effect transistors (DCFETs) is first demonstrated. When compared to the conventional InGaP/InGaAs DCFET, the device with the gate thermal oxide layer exhibits a higher gate turn-on voltage and nearly voltage-independent transconductances as the gate-to-source is biased form −0.75 V to 0 V, while the maximum transconductance is lower. Experimentally, the transconductance within 90% of its maximum value for gate voltage swing is 1.63 V in the gate-oxide device, which is greater than that of 1.35 V in the device without the gate thermal oxide layer. Furthermore, it maintains a high drain current level at negative gate bias in the gate-oxide device, which can be attributed that the thermal oxide layer with a considerably large energy gap absorbs more of gate negative voltage and the influence of negative voltage on the gate depleted thickness is relatively slight.