Microwave performance of InGaAs/InAlAs/InP SISFETs

Microwave S-parameter measurements and equivalent-circuit modeling of In_0.53Ga_0.47As/In_0.52Al_0.48 As/InP semiconductor-insulator-semiconductor FETs (SISFETs) of 1.1-μm gate length are discussed. The devices incorporated wide-bandgap buffers, self-aligned contact implants, and refractory air-bridge gates. Their DC I-V characteristics displayed sharp pinchoff, good output conductance of 10-20 mS/ss, and extrinsic transconductance up to 220 ms/mm at room temperature. The maximum unity-current-gain frequency was 27 GHz. Gate resistance was found to be the dominant factor limiting microwave power gain     

Symmetric P-n-P InAlAs/InGaAs double-heterojunction bipolartransistors fabricated with Si-ion implantation

The authors have successfully fabricated symmetric P-n-P InAlAs/InGaAs double-heterojunction bipolar transistors (DHBTs) using self-aligned Si-ion implantation and refractory emitter contacts with current gains of 115 and 30 in the emitter-up and the emitter-down configurations, respectively. Two thin Be-doped In_0.53Ga_0.47As layers inserted on both sides of base lead to the excellent I-V characteristics. The authors have shown that hole injection from the external portions of the emitter should be suppressed by a factor of 10^-5 to 10^-3 at a collector current density of about 10³ A/cm² , which is much smaller than that of N-p-n GaAs/AlGaAs HBTs and DHBTs are promising devices for applications to circuits with low power dissipation     

DC and microwave characteristics of InAlAs/InGaAssingle-quantum-well MODFETs with GaAs gate barriers

The design and performance of In_0.53Ga_0.47As/In_0.52Al_0.48 As modulation-doped field-effect transistors (MODFETs) have been optimized by incorporating a single In_0.53Ga_0.47As quantum-well channel and a thin strained GaAs gate barrier layer. These help to lower the output conductance and gate leakage current of the device, respectively. The DC performance of 1-μm-gate devices is characterized by extrinsic transconductances of 320 mS/mm at 300 K and 450 mS/mm at 77 K and a best value of f_T=35 GHz is derived from S-parameter measurements     

The influence of gate-feeder/mesa-edge contacting on sidegatingeffects in In0.52Al0.48As/In0.53Ga0.47As heterostructure FET's

Sidegating effects in InAlAs/InGaAs heterostructure field effect transistors (HFETs) were experimentally investigated. Two different configurations of gate feeder across the mesa edges are compared in In _0.52Al_0.48As/In_0.53Ga_0.47As. HFETs. HEMTs and heterostructure insulated-gate FETs (HIGFETs) were fabricated, each with different gate-feeder configurations. HFETs with the gate air bridge over the mesa edge can maintain 99% of the drain-source (I_ds) current level at sidegate voltages (V_sg) extending up to -30 V, while the non-air-bridge configuration of HFETs show a 30% drop of I_ds at the same V _sg. This significant discrepancy of sidegating effect is attributed to depletion region modulation at the mesa edge below the gate feeder. By lifting the gate feeder above the mesa step, sidegating is reduced, which suggests the channel/substrate trap effects are negligibly small. The role of air-bridge structures in determining the sidegating characteristics is discussed     

Electron transport in 0.15-μm gate In0.52Al0.48As/In0.53Ga0.47As HEMT

Magneto-transport and cyclotron resonance measurements were made to determine directly the density, mobility, and the effective mass of the charge carriers in a high-performance 0.15-μm gate In_0.52 Al_0.48As/In_0.53Ga_0.47As high-electron-mobility transistor (HEMT) at low temperatures. At the gate voltage V_G=0 V, the carrier density n _g under the gate is 9×10¹¹ cm^-2, while outside of the gate region n_g=2.1×10¹² cm^-2. The mobility under the gate at 4.2 K is as low as 400 cm²/V-s when V_G<0.1 V and rapidly approaches 11000 cm²/V-s when V_G>0.1 V. The existence of this high mobility threshold is crucial to the operation of the device and sets its high-performance region in V_G>0.1 V     

A new method of determination of the I-Vcharacteristics of negative differential conductance devices bymicrowave reflection coefficient measurements

A technique to map out all of the I-V characteristics of negative differential conductance (NDC) devices is described. This method uses the DC measurable positive conductance portions of the I-V curve together with the measured microwave reflection coefficients at different RF signal levels and fixed DC bias voltage. The advantages of the method for high NDC devices are pointed out in a stability analysis. The complete I-V curve of a tunnel diode has been obtained with an accuracy within 5% in a proof-of-principal test of this method     

A new method of determination of the I-Vcharacteristics of negative differential conductance devices

A method for mapping the complete I-V characteristic of a negative differential conductance (NDC) device has been investigated. This method employs the measurable positive differential conductance (PDC) portions of the DC I-V curve together with the measured conductances at a fixed DC bias voltage in the PDC region with different RF signal levels using a standard semiconductor analyzer. The NDC regime of the I-V curve is numerically constructed from the measured conductances at a fixed DC bias voltage in the PDC region with different signal levels using a large-signal nonlinear-circuit analysis     

Modeling and experimental results for C(V) in anabrupt isotype n Al0.5Ga0.5As/GaAs heterojunction

The differential capacitance C of an abrupt isotype n Al_0.5 Ga_0.5As/GaAs heterojunction has been modeled by directly calculating the dependence of the space charge on the voltage V at its terminals. The electron charge distribution was calculated considering the 2-D electron gas by simultaneously solving the Schrodinger and the Poisson equations, DX centers included. Results from this model predict an asymmetric bell-shape dependence of C on V, with a maximum near the contact potential, and are in good agreement with experiment. This further provides experimental evidence of Γ-Γ and X-X valley coupling for electrons traveling across the heterojunction. For voltage values not too close to the contact potential, it was possible to find a simple method, based on a total depletion, that gives a good fit to experiment     

Near-ideal I-V characteristics of GaInP/GaAsheterojunction bipolar transistors

GaInP/GaAs heterojunction bipolar transistors (HBTs) have been fabricated and these devices exhibit near-ideal I-V characteristics with very small magnitudes of the base-emitter junction space-charge recombination current. Measured current gains in both 6-μm×6-μm and 100-μm×100-μm devices remain constant for five decades of collector current and are greater than unity at ultrasmall current densities on the order of 1×10^-6 A/cm². For the 6-μm×6-μm device, the current gain reaches a high value of 190 at higher current levels. These device characteristics are also compared to published data of an abrupt AlGaAs/GaAs HBT having a base layer with similar doping level and thickness     

A complete model of the I-V characteristics fornarrow-gate MOSFETs

A unified and process-independent MOSFET model for accurate prediction of the I-V characteristics and the threshold voltages of narrow-gate MOSFETs is discussed. It is based on several enhancements of the SPICE2 LEVEL3 MOS model and the author's previous subthreshold I-V model. The expressions achieved for the drain current hold in the subthreshold, transition, and strong inversion regions. A continuous model is proposed for the transition region, using a scheme that ensures that both the current and conductance are continuous and will not cause convergence problems for circuit simulation applications. All of the modeled parameters are taken from experimentally measured I-V characteristics and preserve physical meaning. Comparisons between the measured and modeled I-V characteristics show excellent agreement for a wide range of channel widths and biases. The model is well suited for circuit simulation in SPICE     

Silicon-carbide high-voltage (400 V) Schottky barrier diodes

The authors describe the fabrication and characteristics of the first high-voltage (400-V) silicon-carbide (6H-SiC) Schottky barrier diodes. Measurements of the forward I-V characteristics of these diodes demonstrate a low forward voltage drop of ~1.1 V at an on-state current density of 100 A/cm² for a temperature range of 25 to 200°C. The reverse I-V characteristics of these devices exhibit a sharp breakdown, with breakdown voltages exceeding 400 V at 25°C. In addition, these diodes are shown to have superior reverse recovery characteristics when compared with high-speed silicon P-i-N rectifiers     

Narrow-gate In0.53Ga0.47As junctionfield-effect transistors as tunable resistors for long-wavelengthintegrated optical receivers

The fabrication of In_0.53Ga_0.47As junction field-effect transistors (JFETs) for use as active feedback resistors in integrated transimpedance photoreceivers is described. Transistors using both air-bridge and non-air-bridge technologies are described. Varying the gate-to-source voltage (V_GS) allows the output resistance to be tuned continuously between 3 and 40 kΩ with a drain-to-source shunt capacitance of less than 10 fF. The temperature coefficient of the output resistance is between -5 and -20 Ω/°C (for V_GS less than the pinch-off voltage). The combination of large resistance and low shunt capacitance can result in high receiver sensitivity without sacrificing amplifier dynamic range. The feedback FETs are fabricated adjacent to 1.8-μm gate JFETs with transconductances of 110 mS/mm and gate-to-source capacitances of 1.3 pF/mm     

Light-to-input nonlinearities in an R-LED series network

The light-to-current (L-I) and light-to-voltage (L-V) differential nonlinearities in the simple network of a customary LED and an external resistor R in series are analyzed and calculated theoretically and compared with experimental data. Particular emphasis is placed on the influence of the log-arithmetic slope ν of the L-I characteristic and the bias current I upon the ratio of the corresponding nonlinearity parameters. It is thus deduced that, for a given optical power P, over superlinear portions of the L-I curve (ν>1) the L-I linearity is typically better than its corresponding L-V linearity. On the contrary, when the L-I dependence is sublinear (ν<1) the voltage driving scheme may ensure for the R-LED network, or the LED alone, a local L-V response much more linear than the L-I response, provided that appropriate (optimum) I and/or R values are chosen     

Doubly strainedIn0.41Al0.59As/n+-In0.65Ga0.35As HFET with high breakdown voltage

An In_0.41Al_0.59As/n⁺-In_0.65 Ga_0.35As HFET on InP was designed and fabricated, using the following methodology to enhance device breakdown: a quantum-well channel to introduce electron quantization and increase the effective channel bandgap, a strained In_0.41Al_0.59As insulator, and the elimination of parasitic mesa-sidewall gate leakage. The In_0.65Ga_0.35As channel is optimally doped to N_D=6×10¹⁸ cm^-3. The resulting device (L_g=1.9 μm, W_g =200 μm) has f_t=14.9 GHz, f_max in the range of 85 to 101 GHz, MSG=17.6 dB at 12 GHz V_B=12.8 V, and I_D(max)=302 mA/mm. This structure offers the promise of high-voltage applications at high frequencies on InP     

An analytical model for I-V and small-signalcharacteristics of planar-doped HEMTs

An analytical current-voltage (I-V) model for planar-doped HEMTs is developed. This compact model covers the complete range of I-V characteristics, including the current saturation region and parasitic conduction in the electron-supplying layer. Analytical expressions for the small-signal parameters and current-gain cutoff frequency are derived from the I-V model. Modeling results for a 0.1-μm-gate planar-doped AlInAs-GaInAs HEMT show excellent agreement with measured characteristics. Threshold voltages and parasitic conduction in planar-doped and uniformly doped HEMTs are also compared and discussed     

Low-frequency noise characteristics of lattice-matched(x=0.53) and strained (x>0.53) In0.52Al0.48As/InxGa1-xAs HEMT's

Extensive bias-dependent and temperature-dependent low-frequency (LF) noise measurements were performed on lattice-matched and strained In_0.52Al_0.48As/In_xGa_1-x As(0.53<x<0.70) HEMTs. The input-noise voltage spectra density is insensitive to V_DS bias and shows a minimum at V_GS corresponding to the peak g_m condition. The corresponding output-noise voltage spectral density, which depends strongly on the gain of the devices, increases with V_DS. The input noise was rather insensitive to indium (In) content. Temperature-dependent low-frequency noise measurements on these devices reveal shallow traps with energies of 0.11, 0.15, and 0.18 eV for 60%, 65%, and 70% In HEMTs. Noise transition frequencies for these devices were on the order of 200-300 MHz and remain almost the same for different channel In content and V_DS bias     

SPICE macro model for the simulation of zener diodeI-V characteristics

The problems encountered when using the existing SPICE diode model to represent the I-V characteristics of a Zener diode in the reverse region are examined. A Zener diode macro model that has accurate I-V simulation characteristics and can be easily constructed using SPICE-provided primitives is presented. The static I-V characteristics and temperature response of the diode are reviewed. The performance of the model is discussed, and its main enhancements as compared to the SPICE model are identified     

PV module characterization using Q-Rdecomposition based on the least square method

The determination of solar cell parameters (I-V characteristic) from experimental data was achieved by using the Q -R decomposition technique based on the least squares method, where all data points were considered. The algorithm used a three-parameter equation transformed from the original cell equation of five parameters. This method could be used to analyze the I-V characteristics of photovoltaic (PV) modules of various technologies under the natural conditions of implementation, and to help to establish the best sizing of a PV system and the best adaptation of a PV system to its environment     

Monte Carlo study of GaAs/Alx Ga1-xAsMODFETs: effects of AlxGa1-xAs composition

Monte Carlo methods are used to compare electronic transport and device behavior in n⁺-Al_xGa_1-xAs/GaAs modulation-doped field-effect transistors (MODFETs) at 300 K for x =0.10, 0.15, 0.22, 0.30, 0.35, and 0.40. The differences between the x=0.22 and x=0.30 MODFETs with respect to parasitic conduction in Al_xGa_1-xAs, gate currents, and switching times, are of particular interest. The donor-related deep levels in Al_xGa_1-xAs, are disregarded by assuming all donors to be fully ionized, and the focus is only on the confinement and transport of the carriers. The following quantities are studied in detail: transfer characteristics (I_D versus V _G), transconductance (g_m), switching speeds (τ_ON), parasitic conduction in Al_xGa _1-xAs, gate current (I_G), average electron velocities and energies in GaAs and Al_xGa_1-x As, electron concentration in the device domain, k-space transfer (to low mobility L and X valleys), and details of the real-space transfer process     

In0.52Al0.48As/In0.53Ga0.47As MSM photodetectors and HEMT's grown by MOCVD on GaAs substrates

The authors report the first demonstration of In_0.52Al _0.48As/In_0.53Ga_0.47As metal-semiconductor-metal (MSM) photodetectors and high-electron-mobility transistors (HEMTs) grown on GaAs substrates by organometallic chemical vapor deposition. Both photodetectors and transistors showed no degradation in performance compared to devices simultaneously grown on InP substrates. The photodetectors exhibited a responsivity of 0.45 A/W and leakage current of 10 to 50 nA. The HEMTs with a gate length of 1.0 μm showed a transconductance as high as 250 mS/mm, and f_T and f_max of 25 and 70 GHz, respectively