High-speed Ga0.47In0.53As/InP infra-redSchottky-barrier photodiodes

The authors report a new high-speed InP-based Ga_1-xIn _xAs infra-red Schottky-barrier photodiode. The photodiodes were fabricated on both p- and n-GaInAs epilayers using Schottky barrier height enhancement technology. The response speed was measured by the impulse response and autocorrelation method; the risetimes of 85 ps for p-GaInAs and 180 ps for n-GaInAs photodiodes were obtained, which correspond to the 3 dB cutoff frequency of 2-4 GHz. The intrinsic response speed was 12 GHz for n-GaInAs and 18 GHz for p-GaInAs photodiodes based on SPICE simulation with measured device parameters. The photodiodes had the responsivity as high as 0.55 A/W and the quantum efficiency of up to 45% at 1.3-1.6 μm without antireflection coating     

High-speed Ga0.47In0.53As MISIMphotodetectors with dielectric-assisted Schottky barriers

A technique is described for fabricating high-speed metal-insulator-semiconductor-insulator-metal (MISIM) photodetectors for high-speed fiber-optic systems. These devices make use of a Langmuir-Blodgett film enhanced Schottky barrier to achieve broadband linear response to 13 GHz at low bias voltage (5 V) with ~0.9 A/W external responsivity, 15 V breakdown voltage, and ~2 μA dark current. A gain of about 2 and a 5% tail in the temporal response are analyzed. The needed bias and the device processing are compatible with those for integrated receivers     

Al0.48In0.52As/Ga0.47In0.53As resonant tunnelling diodes with large current peak/valley ratio

Resonant tunnelling diodes consisting of an MBE-grown AlInAs barrier on each side of a lattice-matched GaInAs well have been fabricated. Current peak/valley ratios up to 7.1 and 39 have been measured at 300 K and 77 K, respectively. These represent the largest values reported to date in any double-barrier, single-well device. The enhanced peak/valley ratio has been attributed to thick barriers (72 Å) and wide, undoped GaInAs spacer layers (400 Å)     

Low-temperature DC characteristics of pseudomorphic Ga0.18In0.82P/InP/Ga0.47In0.53As HEMT

A high-gap strained GaInP material chosen to increase Schottky barrier height on InP is discussed. This material has been used for the first time in high electron mobility transistor (HEMT) fabrication on InP. For these devices the best g_m of a 1.3-μm gate HEMT is 300 mS/mm. Transistors of 3-μm gate length are studied at low temperature (100 to 293 K). Their DC electrical characteristics improve upon cooling. The best improvement is measured at the lowest temperature (+54% for g_m at 105 K). The structure is stable and does not present any g_m or I_ds collapse at low temperature, unlike AlGaAs/GaAs heterostructures     

Resonant tunnelling in Ga0.47In0.53As/InPdouble-barrier structures grown by AP-MOCVD

Reports the first observation of negative-differential resistance in Ga_0.47In_0.53As/InP double-barrier structures grown by AP-MOCVD. The devices exhibit the largest peak/valley current ratios seen in this system; 1.2:1 (2.8:1) and 3.0:1 (5.5:1) at 77 K (4.2 K) for the n=1 and n=2 resonances respectively     

High peak tunnel current densityGa0.47In0.53As Esaki diodes

High peak current density Ga_0.47In_0.53As interband tunnel diodes were fabricated by metal organic molecular beam epitaxy. A room temperature peak-to-valley current ratio of 16 and a peak tunnel current density of 9.2 kA/cm² were obtained in diodes doped to ~3×10¹⁹cm³ on both n-type and p-type sides. A peak-to-valley current ratio of 3.8, and a peak tunnel current density of 93.2 kA/cm² were obtained in diodes doped to ~10²⁰ cm^-3 on both n-type and p-type sides     

Proton bombardment in n- and p-type Ga0.47In0.53As

Ga_0.47In_0.53As epitaxial layers on InP substrate have been subjected to proton bombardment. The resistivity increases up to 10⁴Ω cm for 10¹⁴H⁺/cm² in p-type and 3 · 10¹⁶H⁺/cm² in n-type a_0.47In_0.53As implanted at 77 K. Proton bombardment at 300 K showed this increase in resistivity only for p-type material. Channeling experiments indicated that the damage of the lattice which seems to be responsible for the resistivity increase of n-material can be produced only at low temperature with doses of the order of 10¹⁶H⁺/cm². Crystalline layers implanted with high dose showed blistering effects after heat treatments.     

Disordering of Ga0.47In0.53As/InP multiplequantum well layers by sulphur diffusion

The disordering of Ga_0.47In_0.53As/InP MQW layers by the diffusion of sulphur is reported for the first time. Photoluminescence measurements indicate that this results in a larger bandgap material. SIMS profiles show that intermixing of both group III and V elements occurs between wells and barriers     

Ga0.47In0.53As metal-semiconductor-metalphotodiodes using a lattice mismatchedAl0.4Ga0.6As Schottky assist layer

Metal-semiconductor-metal photodiodes (MSM PDs) with Ga_0.47 In_0.53As active layers were fabricated. The low Schottky barrier height of GaInAs was overcome by the insertion of a lattice mismatched AlGaAs intermediary layer between metal and GaInAs active layer. Fabricated MSM PDs utilising interdigitated metal electrodes formed by a self-alignment technique showed a fast rise and fall time of 650 ps, which was limited by the capacitance of the device. The gain of the device was less than 1     

High-transconductance heterostructure Ga0.47In0.53As/InP metal-insulator-semiconductor field-effect transistorsgrown by chemical beam epitaxy

SiO₂ insulator is on top of an InP layer; current transport occurs, however, an in adjacent n-type Ga_0.47In_0.53As:Sn layer. A transconductance of g_m=300 mS/mm is obtained from depletion-mode MISFETs with a gate length of 1.2 μm. This MIS (metal-insulator-semiconductor) junction has a symmetric current-voltage characteristic and a low-leakage current of ~1 nA at ±2 V. High-frequency S-parameter measurements performed b probing devices on the wafers yield a unity current gain frequency of F _t=22.2 GHz and a maximum frequency of oscillation f _max=27 GHz     

Relaxation of hot carriers in undoped and n-doped Ga0.47In0.53As generated by subpicosecond pulses

The cooling process of hot carriers in bulk Ga_0.47In_0.53As at 30 K is studied with subpicosecond time resolution. The time-dependence of the sample transmission at a wavelength of 1265 nm is measured after the generation of charge carriers with an excess energy ω-E_g in the order of 200 meV and at densities of up to 7 × 10¹⁷ cm⁻³. In an undoped sample, an almost double-exponential relaxation of the transmission change is found with time constants of about 1 ps and 10 ps, respectively. In contrast, a nearly single-exponential time behavior is observed in a n-doped sample with a time constant of 3 ps. The experimental data agree well with the results of model calculations that do not take into account “hot” phonon reabsorption by the carriers. The model reproduces the approximately double-exponential transmission relaxation of the undoped sample. The two time constants can be attributed to the population change of either the conduction or the heavy hole valence band states that are probed by the light pulses. The experimental data can be explained without assuming different temperatures of the electrons and the holes during the cooling process.     

High mobility two-dimensional electron gas inInP/Ga0.47In0.53As heterojunctions grown bylow-pressure organometallic vapour phase epitaxy

The two-dimensional electron gas in InP/GaInAs heterojunctions, grown by LP-OMVPE, showed Hall mobilities as high as 164000 and 103000 cm²/Vs at 4 K and 80 K, respectively. A maximum Hall mobility of 172000 cm²/Vs was measured at 20 K. Shubnikov-de Haas oscillations measured at 200 mK in magnetic fields up to 20 T indicated the total absence of parallel conduction. By illuminating the sample it was possible to populate the second electrical sub-band at a total carrier density n_s=4.4×10¹¹ cm^-2     

Diffusion-induced disordering ofGa0.47In0.53As/InP multiple quantum wells withzinc

Diffusing zinc into Ga_0.47In_0.53As/InP MQW layers is found to cause strong intermixing of the group III elements, which changes the composition in the quantum wells and barriers. As a result of this disordering the MQW bandgap is reduced in energy and the photoluminescence emission peak moves to longer wavelength     

High-frequency submicrometerAl0.48In0.52As/In0.53Ga0.47As heterostructure bipolar transistors

The high speed scaling of an Al_0.48In_0.52As/In_0.53Ga_0.47 As submicrometer heterostructure bipolar transistor (HBT) is presented. Transistors with emitter dimensions of 0.5×11 and 3.5×3.5 μm² exhibit unity current-gain cutoff frequencies of 63 and 70 GHz, respectively. Emitter current density greater than 3.3×10⁵ A/cm² is demonstrated in a submicrometer AlInAs/InGaAs HBT. The analysis shows that the device speed is limited by the parasitic collector charging time     

Enhancement mode metamorphicAl0.67In0.33As/Ga0.66In0.34As HEMT on GaAs substrate with high breakdown voltage

This paper presents original and experimental results provided by E-mode Al_0.67In_0.33As/Ga_0.66In_0.34 As metamorphic HEMT. The devices exhibit good dc and rf performances. The 0.4 μm gate length devices have saturation current density of 355 mA/mm at +0.6 V gate-to-source voltage. The Schottky characteristic is a typical reverse gate-to-drain breakdown voltage of -16 V. It is the first time, to our knowledge, that gate current issued from impact ionization have been observed in these devices versus gate to drain extension. These results are the first reported for E-mode Al _0.67In_0.33As/Ga_0.66In_0.34As MM-HEMTs on GaAs substrate     

Hot-electron transport in In0.53Ga0.47As

A set of physical constants for In_0.53Ga_0.47As as required for transport calculations is obtained by reviewing the literature. Velocities for fields up to 100 kV/cm, calculated by the Monte Carlo method using these constants, are presented for the temperatures of 95 and 300 K. The calculated values are found to be in good agreement with the available experimental results.     

Enhancement-mode Al0.66In0.34As/Ga0.67In0.33As metamorphic HEMT, modeling and measurements

This paper exhibits experimental and theoretical results on metamorphic high-electron mobility transistor (MM-HEMT). Modeling and measurements provide a better knowledge of device physics which allows us to optimize device structures. We present 10-GHz power performances, pulse and gate measurements, and two-dimensional (2-D) hydrodynamic modeling of enhancement-mode (E-mode) Al_0.66In_0.34As/Ga_0.67In_0.33 As NM-HEMT devices. It is the first time that cap layer thickness has been studied for a MM-HEMT. A typical reverse breakdown voltage of 16 V has been obtained. Gate current issued from impact ionization has been shown, for the first time, in such a device. The 2-D hydrodynamic model is a useful tool for cost engineering because it brings more information in terms of physical quantity distributions, necessary to predict breakdown behavior of FET. The 10-GHz measurements with a load-pull power set-up demonstrate the capabilities for a thick cap device with large gate-to-drain extension since an output power of 140 mW/mm have been obtained which is the state-of-the-art for such a device. These results obtained confirm the great interest of the structures for power application systems. The only work reported, to our knowledge, using a MM-HEMT structure in E-mode with an indium content close to 50% has been studied by Eisenbeiser et al.. Their typical gate-to-drain breakdown voltage was 5.2 V. The 0.6 μm ×3 mm devices exhibited 30 mW/mm at 850 MHz     

A resistive-gate In0.53Ga0.47As/InPheterostructure CCD

The first InGaAs/InP charge-coupled device (CCD) is demonstrated, exhibiting a charge transfer efficiency (CTE) of 0.98 at 13 MHz and 1 GHz. Cooling the device improves the CTE to greater than 0.99 at 13-MHz clock frequency. The 0.76-eV In_0.53Ga_0.47As bandgap makes this structure applicable to direct-detection short-wavelength infrared (SWIR) imagers     

25.5% efficient Ga0.35In0.65P/Ga0.83In0.17As tandem solar cells grown on GaAs substrates

Theoretical calculations predict a higher power conversion efficiency for the combination of Ga_0.35In_0.65P and Ga_0.83In_0.17As in a tandem solar cell, compared to the more commonly used Ga_0.51In_0.49P/GaAs approach. A record conversion efficiency of 21.6% (AM1.5 g) was recently achieved for a 1.18 eV Ga_0.83In_0.17As solar cell, grown lattice-mismatched to the GaAs substrate material. This paper reports on the device characteristics of first Ga_0.35In_0.65P/Ga_0.83In_0.17As tandem solar cells based on this very promising GaInAs material. A high quantum efficiency, comparable to the lattice-matched Ga_0.51In_0.49P on GaAs approach was achieved. A power conversion efficiency of 25.5% was measured under AM1.5d spectral conditions     

MetamorphicIn0.53Ga0.47As/In0.52Al0.48As HEMTs on germanium substrates

We report for the first time the successful epitaxial growth and processing of high-performance metamorphic high electron mobility transistors (HEMTs) on Ge substrates, with a transconductance of 700 mS/mm and a saturation channel current of 650 mA/mm. To reduce parasitic capacitances due to the conductive substrate, a dry etch method based on CF₄ and O₂ reactive ion etching (RIE) is developed for selective substrate removal. Devices with 0.2 μm gate length display an increase of the extrinsic cut-off frequency f_T from 45 GHz before, to 75 GHz after substrate removal, whereas the maximum oscillation frequency f_max increases from 68 GHz to 95 GHz. Based on this excellent rf performance level, in combination with the highly selective thinning process, we think that Ge as a sacrificial substrate is a promising candidate for the integration of thinned individual HEMTs with passive circuitry on low-cost substrates. This could result in low-cost advanced hybrid systems for mass-market millimeter wave applications