Investigation of negative differential resistance phenomena inGaSb/AlSb/InAs/GaSb/AlSb/InAs structures

The negative differential resistance (NDR) phenomena were observed in GaSb/AlSb/InAs/-GaSb/AlSb/InAs resonant interband tunnel structures. Electrons have resonantly achieved interband tunneling through the InAs/GaSb broken-gap quantum well. The InAs well width causes significant variations of the peak current density and NDR behaviors. The peak current density varies exponentially with the AlSb barrier thickness. The multiple NDR behavior was observed with appropriate InAs well and AlSb barrier thicknesses, e.g., 30 Å thick AlSb barrier and 240 Å wide InAs well. Only single negative resistance has, otherwise, been seen. The three-band model was used to interpret the effect of the InAs well and AlSb barrier on the current-voltage characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs structures     

Effects of layer design on the performance of InAs/AlSb/GaSb resonant interband tunneling diodes on GaAs substrates

The room temperature current-voltage characteristics of InAs/AlSb/GaSb resonant interband tunneling diodes (RITDs), grown by chemical beam epitaxy on GaAs substrates, are reported as a function of the InAs buffer layer thickness and different interface configurations. The peak-to-valley current ratio (PVCR) improved from 1 to 12 as the buffer thickness was increased from 0 to 500 nm and the density of dislocations caused by the lattice mismatch of ∼7% decreased. No significant improvement was seen for a buffer thickness beyond 500 nm. Dislocation-free RITDs, grown lattice-matched on InAs substrates, show PVCRs of approximately 16. The InAs/AlSb Interfaces in these structures can be either InSb-like or AlAs-like and the interface can have a very strong effect on the diode performance. Unlike the case in InAs/AlSb field effect transistor structures, an AlAs-like interface results in better PVCRs in the diodes. Details of the results of this study are presented.     

InAs/AlSb/GaSb resonant interband tunneling diodes andAu-on-InAs/AlSb-superlattice Schottky diodes for logic circuits

Integrated resonant interband tunneling (RIT) and Schottky diode structures, based on the InAs/GaSb/AlSb heterostructure system, are demonstrated for the first time. The RIT diodes are advantageous for logic circuits due to the relatively low bias voltages (~100 mV) required to attain peak current densities in the mid-10⁴ A/cm ² range. The use of n-type InAs/AlSb superlattices for the semiconducting side of Schottky barrier devices provides a means for tailoring the barrier height for a given circuit architecture. The monolithically integrated RIT/Schottky structure is suitable for fabrication of a complete diode logic family (AND, OR, XOR, INV)     

Microwave performance and modeling of InAs/AlSb/GaSb resonantinterband tunneling diodes

The microwave frequency performance of InAs/ AlSb/GaSb resonant interband tunneling diodes has been examined experimentally. A bias-dependent small-signal circuit model that matches the measured data well for the full range of measured frequencies (dc to 35 GHz) and the full range of device biases (0 to 0.5 V) has been obtained. To the author's knowledge, this is the first report of a microwave-frequency circuit model that is valid over the full range of device operating biases, including the negative differential resistance region. The bias dependence of the circuit elements contained within the model is examined, and is consistent with device operational principles     

Static random access memories based on resonant interband tunnelingdiodes in the InAs/GaSb/AlSb material system

We have fabricated SRAM's based on resonant interband tunneling diodes in the InAs/AlSb/GaSb material system. The bistability and the switching principles are demonstrated. Numerical simulations of the memory characteristics of the SRAM cell are performed and used for comparing with experiments. Several key issues involving the applications of the device are also discussed     

Investigation of the influence of the well and the barrierthicknesses in GaSb/AlSb/GaSb/AlSb/InAs double-barrier interbandtunneling structures

The tunneling currents of GaSb/AlSb/GaSb/AlSb/InAs double-barrier interband tunneling (DBIT) structures were studied experimentally by varying the thickness of the well and the barrier layers systematically. The optimal thicknesses for the GaSb well and the AlSb barriers were found to be 6.5 and 1.0 nm, respectively, to obtain a high peak current density (19 kA/cm²), with a large peak-to-valley ratio of 4. The high peak current in the DBIT structure shows the strong effect of the resonant coherence of the wave function across the double barrier. For the case of a small GaSb well width (3 nm), a drastic reduction of the peak current was observed, an effect suggesting that the electron-wave function in the InAs couples primarily to the quantized light hole state in the GaSb well     

Population inversion in two-dimensional InAs/GaSb/AlSb systems

We analyse the potentiality of InAs/GaSb/AlSb tunnel structures for creation of the population inversion and stimulated radiation both in the presence and in the absence of magnetic field.     

A complementary heterostructure field effect transistor technologybased on InAs/AlSb/GaSb

A complementary heterojunction field effect transistor technology based on the InAs/AlSb/GaSb system is proposed. The structure is formed by the vertical integration of InAs n-channel and GaSb p-channel HFET devices. The superior transport properties of electrons in InAs and holes in GaSb and their band offsets to AlSb or AlSbAs yield devices with transconductances much greater than AlGaAs/GaAs n- and p-channel HFETs. It is shown that a complementary circuit fabricated from these devices could provide room-temperature performance up to six times greater than that predicted for AlGaAs/GaAs complementary circuits     

Intersubband Raman scattering in InAs/AlSb quantum wells

Raman spectroscopy has been used to study intersubband transitions in InAs/AlSb single quantum wells grown by molecular-beam epitaxy on (100) GaAs substrates using strain-relaxed AlSb or GaSb buffer layers. From the measured energies of the coupled longitudinal optical phonon-intersubband plasmon modes the single particle transition energies between the first and second confined electron subbands were deduced as a function of the width of the pseudomorphically strained InAs well. Subband spacings calculated including the effects of strain and nonparabolicity were found to be in agreement with the experimental transition energies. For a given well width, the two-dimensional electron concentration deduced from the Raman measurements was found to be lower than the concentration measured in the dark by Hall effect, but showed a significant increase with increasing optical excitation intensity.     

Unintentional As incorporation in molecular beam epitaxially grown InAs/AlSb/GaSb heterostructures

We investigate unintentional arsenic incorporation during the molecular-beam epitaxial growth of AlSb/InAs/GaSb heterostructures, using both a standard As₄ evaporation cell and a valved arsenic cracker. When a standard As₄ cell is used, unintentional arsenic concentrations as large as 10–20% can be incorporated into the AlSb and GaSb layers from the background As ambient in the growth chamber, both during growth and on stationary surfaces. This incorporation can be controlled and suppressed with the use of a valved As cracker. Suppression of the As background substantially improves the electrical transport properties of AlSb/InAs/AlSb quantum well structures.     

Exchange-induced band hybridization in InAs/GaSb based type II and broken-gap quantum well systems

We demonstrate theoretically that the many-body effect such as exchange interaction can cause the hybridization of the electron and hole dispersion relations in InAs/GaSb based type II and broken-gap quantum well (QW) systems. As a result, a terahertz mini-gap at the anti-crossing points of the conduction and valence bands can be induced by the inter-layer electron–hole coupling via the Coulomb interaction. It is shown that the many-body effect is another important source of the hybridization of the dispersion relations in InAs/GaSb QW systems.     

Digital integrated circuit using integrated InAlAs/InGaAs/InP HEMTsand InAs/AlSb/GaSb RITDs

The demonstration of the first integrated circuit using monolithically integrated InAs/AlSb/GaSb resonant interband tunnelling diodes (RITDs) and InAlAs/InGaAs/InP high electron mobility transistors (HEMTs) is reported. A D-flip-flop (D-FF) was implemented using the monostable/bistable logic element (MOBILE) circuit architecture, with a measured effective voltage gain in excess of 380. Power dissipation of less than 2.8 mW/gate was measured     

InAs/AlSb dual-gate HFETs

We report the first implementation of InAs/AlSb dual-gate (DG) HFETs. The devices were fabricated by conventional optical lithography and consist of two electrically distinct 1-μm gates, with a 1-μm intergate separation. The DG-HFETs feature well-behaved, kink-free drain characteristics, and exhibit both high transconductance and low output conductance. We find that DG operation significantly reduces the short-channel effects that have so far plagued InAs/AlSb devices, and increases the maximum allowable drain bias. We estimate that cutoff frequencies as high as 30 GHz-μm may be possible for such devices based on simple equivalent circuit models and previously published experimental data on single-gate InAs/AlSb HFETs     

Effect of lattice-mismatched growth on InAs/AlSb resonant-tunnelingdiodes

Nominally identical InAs/AlSb resonant-tunneling diodes are fabricated on InAs and GaAs substrates to ascertain the effect of dislocations on the resonant-tunneling process. Although the diode on the GaAs substrate had a much higher dislocation density, as evidenced by X-ray diffraction measurements, it displayed only a small decrease in peak-to-valley current ratio     

Transition from the type-II broken-gap heterojunction to the staggered one in the GaInAsSb/InAs(GaSb) system

Conditions for the transition from the staggered heterojunction to the type-II broken-gap one were considered for isolated Ga_1?x In_xAs_ySb_1?y /InAs(GaSb) heterostructures in relation to the quaternary alloy composition. Energy-band diagrams of such heterojunctions were estimated and energy band offsets Δ at the heterointerface were determined. It was experimentally found that the type-II broken-gap heterojunction in the Ga_1?x In_xAs_ySb_1?y /p-InAs structure is observed in the entire range of composition parameters under study, 0.03 < x < 0.23, and becomes staggered in the range 0.3 < x < 1. In p-Ga_1?x In_xAs_ySb_1?y /p-GaSb heterostructures with the indium content 0.85 < x < 0.92 in the solid phase, the p-type conductivity is observed, which is indicative of the staggered heterojunction. At x > 0.92, the contribution of electrons of the semimetal channel at the heterointerface to the total conductivity was observed, as well as the transition from the staggered heterojunction to the type-II broken-gap one.     

Vertical transport in type-II heterojunctions with InAs/GaSb/AlSb composite quantum wells in a high magnetic field

Vertical transport in type-II heterojunctions with a two-barrier AlSb/InAs/GaSb/AlSb quantum well (QW) grown by MOVPE on an n-InAs (100) substrate is investigated in quantizing magnetic fields up to B = 14 T at low temperatures T = 1.5 and 4.2 K. The width of the QWs is selected from the formation condition of the inverted band structure. Shubnikov–de Haas oscillations are measured at two orientations of the magnetic field (perpendicular and parallel) relative to the structure plane. It is established that conduction in the structure under study is occurs via both three-dimensional (3D) substrate electrons and two-dimensional 2D QW electrons under quantum limit conditions for bulk electrons (B > 5 T). The electron concentrations in the substrate and InAs QW are determined. The g-factor for 3D carriers is determined by spin splitting of the zero Landau level. It is shown that the conductance maxima in a magnetic field perpendicular to the structure plane and parallel to the current across the structure in fields B > 9 T correspond to the resonant tunneling of 3D electrons from the emitter substrate into the InAs QW through the 2D electron states of the Landau levels.     

Gate-Recess Technology for InAs/AlSb HEMTs

The gate-recess technology for Si $delta$-doped InAs/AlSb high-electron-mobility transistors (HEMTs) has been investigated by combining atomic force microscopy (AFM) inspection of the gate-recess versus time with electrical device characterization. Deposition of the gate metal on the $hbox{In}_{0.5}hbox{Al}_{0.5}hbox{As}$ protection layer or on the underlying AlSb Schottky layer resulted in devices suffering from high gate-leakage current. Superior dc and high frequency device performance were obtained for HEMTs with an insulating layer between the gate and the Schottky layer resulting in a reduction of the gate leakage current $I_{G}$ by more than two orders of magnitude at a drain-to-source voltage $V_{DS}$ of 0.1 V. The existence of this intermediate insulating layer was evident from the electrical measurements. AFM measurements suggested that the insulating layer was due to a native oxidation of the AlSb Schottky layer. The insulated-gate HEMT with a gate length of 225 nm exhibited a maximum drain current $I_{D}$ higher than 500 mA/mm with good pinchoff characteristics, a dc transconductance $g_{m}$ of 1300 mS/mm, and extrinsic values for cutoff frequency $f_{T}$ and maximum frequency of oscillation $f_{max}$ of 160 and 120 GHz, respectively.      

A W-band InAs/AlSb low-noise/low-power amplifier

The first W-band antimonide based compound semiconductor low-noise amplifier has been demonstrated. The compact 1.4-mm/sup 2/ three-stage co-planar waveguide amplifier with 0.1-/spl mu/m InAs/AlSb high electron mobility transistor devices is fabricated on a 100-/spl mu/m GaAs substrate. Minimum noise-figure of 5.4dB with an associated gain of 11.1 dB is demonstrated at a total chip dissipation of 1.8 mW at 94 GHz. Biased for higher gain, 16/spl plusmn/1 dB is measured over a 77-103 GHz frequency band.     

InAs/GaSb台面结型器件制备工艺技术研究

随着红外探测技术的不断进步,第三代红外探测器的发展需求日渐明晰。由于带间跃迁工作原理、暗电流抑制效应以及成熟的材料制备技术基础等因素,InAs/GaSb超晶格材料已经成为了第三代红外焦平面探测器的首选制备材料。基于InAs/GaSb超晶格材料的台面结型焦平面器件制备方法主要包括湿法腐蚀技术、干法刻蚀技术以及干湿法结合技术。从文献调研结果来看,湿法腐蚀技术和干法刻蚀技术各有优缺点。湿法腐蚀技术适用于单元以及少像元面阵的制备,其中磷酸系腐蚀液的腐蚀效果最佳;干法刻蚀技术适用于大面阵、小尺寸焦平面阵列的制备,几种氯基刻蚀气体体系以及氯基与甲烷基组合的刻蚀气体体系都表现出了不错的刻蚀效果;干湿法结合技术在干法刻蚀后引入湿法腐蚀工艺以进一步消除刻蚀损伤,从而提高器件性能。对以上三种技术方案进行了介绍和分析。     

Optical properties of heterostructures with deep AlSb/InAs0.84Sb0.16/AlSb quantum wells

Using the Kane model, the energy of the dimensional quantization levels, absorption coefficient, and radiative-recombination rate are calculated for interband optical transitions between different dimensional quantization subbands in a heterostructure with a deep AlSb/InAs_0.86Sb_0.14/AlSb quantum well with regard to and without regard for the spin-orbit interaction. It is shown that the corrections introduced by the spin-orbit interaction in calculating these quantities are no larger than a few tens of percent even at spin-orbit interaction constants exceeding the band gap and account for the nonparabolicity in the calculation of the energy of dimensional quantization levels and absorption coefficient is much more important than account for the spin-orbit interaction. In calculation of the radiative-recombination rate, both these effects should be taken into account.