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An empirical large-signal III-V field-effect transistor (FET) model has been developed. Three improved drain-source current (I-V) modeling equations capable of representing arbitrarily shaped transconductance (Gm) curves are proposed from level-i to level-3. These models are characterized by the static dc and the multibias pulsed I-V measurements along with their dependences on temperature, so as to account for the frequency dispersion and the self-heating effects. By partitioning the Gm plots into five regions, specific parameters of the various model levels can be directly associated with the regions. Besides, the fitting parameters have inherent consistent definitions among different model levels, where some of the key model parameters canbe extracted directly from measurements. For the gate-charge formulation (Q-V), a novel charge-conservative gate charge model is presented to accurately trace the nonlinear gate-source (Cgs) and gate-drain (Cgd) capacitance values. The comprehensive large-signal model is then validated by comparing the predicted I-V, C-V, S-parameters as well as power characteristics with the measured results of III-V FETs. [ABSTRACT FROM AUTHOR]

Presents the scaling of noise and small-signal parameters of InP double heterojunction bipolar transistors (DHBT) with high direct current gain. Technique used to derive the noise parameters for a large-size emitter DHBT; Noise model of a large-size emitter DHBT; Verification of the equations derived for the scaling of noise and small-signal parameters.

Examines transformation of the noise and Z-parameters between common emitter and base InP double-heterojunction bipolar transistor. Assessment of the oscillation frequency; Application of the broad-band impedance matching; Observation of the optimum input admittance.

Assesses the viability of InP metamorphic InP heterojunction bipolar transistors (MM-HBT) fabricated on a GaAs substrate. Details on the microwave noise and power performance of InP MM-HBT; Aspects of lattice-matched InP heterojuction bipolar transistors; Demonstration of superior microwave noise and power performance of GaAs HBT.

Provides information on a study which investigated the base current transient in InP/InGaAs heterojunction biporal transistors induced by polyimide passivation. Experiments; Results and discussion; Conclusion.

The effect of post-deposition annealing on chemical bonding states at interface between Al0.5Ga0.5N and ZrO2 grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2p and Ga-O/Ga 3d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to "clean up" effect of ALD-ZrO2 on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through "clean up" effect near the interface. However, degradation of ZrO2/AlGaN interface quality due to re-oxidation at higher annealing temperature (>500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO2/AlGaN interface are easier to get oxidized as compared with Ga atoms. [ABSTRACT FROM AUTHOR]

Influence of post-deposition annealing on interfacial properties related to the formation/annihilation of interfacial GaOx layer of ZrO2 grown by atomic layer deposition (ALD) on GaN is studied. ZrO2 films were annealed in N2 atmospheres in temperature range of 300°C to 700°C and analyzed by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that Ga-O bond to Ga-N bond area ratio decreases in the samples annealed at temperatures lower than 500°C, which could be attributed to the thinning of GaOx layer associated with low surface defect states due to "clean up" effect of ALD-ZrO2 on GaN. However, further increase in annealing temperature results in deterioration of interface quality, which is evidenced by increase in Ga-O bond to Ga-N bond area ratio and the reduction of Ga-N binding energy. [ABSTRACT FROM AUTHOR]

High microwave-noise performance is realized in AIGaN/GaN metal-insulator semiconductor high-electron mobility transistors (MISHEMTs) on high-resistivity silicon substrate using atomic-layer-deposited (ALD) Al2O3 as gate insulator. The ALD Al2O3/AIGaN/GaN MISHEMT with a 0.25-μm gate length shows excellent microwave small signal and noise performance. A high current-gain cutoff frequency fT of 40 GHz and maximum oscillation frequency fmax of 76 GHz were achieved. At 10 GHz, the device exhibits low minimum-noise figure (NFmin) of 1.0 dB together with high associate gain (Ga) of 10.5 dB and low equivalent noise resistance (Rn) of 29.2 π. This is believed to be the first report of a 0.25-nm gate-length GaN MISHEMT on silicon with such microwave-noise performance. These results indicate that the AIGaN/GaN MISHEMT with ALD Al2O3 gate insulator on high-resistivity Si substrate is suitable for microwave low-noise applications. [ABSTRACT FROM AUTHOR]

GaN-on-Si high electron mobility transistors (HEMTs) with 80 nm gate length fabricated using Si CMOS-compatible Ta/Al ohmic and Ti/Al gate contacts are reported in this work. The device with a source–drain distance (Lsd) of 750 nm exhibited a high cut-off frequency (fT) of 210 GHz. A three-terminal off-state breakdown voltage (BVds) of 46 V and a high Johnson’s figure-of-merit (=fT × BVds) of 8.8 THz V have been achieved in a device with Lsd of 1.5 μm. These results show the great potential of GaN-on-Si HEMTs to realize high-performance-to-cost ratio mm-wave devices through mass production using current Si foundries. [ABSTRACT FROM AUTHOR]

A deeply-scaled GaN-on-Si high electron mobility transistor with a record-high cut-off frequency (fT) of 310 GHz has been demonstrated. The device has an InAlN/GaN heterojunction structure, a source–drain spacing of 400 nm, and a gate length of 40 nm. The device exhibited a high drain current of 2.34 A mm−1, a peak transconductance of 523 mS mm−1, and a gate-to-drain breakdown voltage (BVgd) of 15 V. A Johnson’s figure-of-merit (FOM = fT × BV) of 4.65 THz V has been achieved, which is comparable to those reported in GaN-on-SiC. These results indicate GaN-on-Si transistors are promising in low-cost emerging mm-wave applications. [ABSTRACT FROM AUTHOR]

We have proposed and successfully demonstrated a novel and simple process to fabricate self-aligned emitter passivation ledges for heterojunction bipolar transistors (HBTs) without using additional dielectric etch masks or dual etch-stop layers in the emitter. In this new ledge formation process, the emitter ledges are fabricated by the formation of photoresist sidewall spacers followed by a wet-chemical etch process. The effectiveness of this new ledge formation technology has been confirmed in AlGaAs/GaAs HBTs. Since the proposed ledge technology is very simple and without using any etch-stop layers (thus independent of material systems), it appears to be very promising for HBT fabrication. [ABSTRACT FROM AUTHOR]

The microwave noise performances of metamorphic (MM) InP/In0.53Ga0.47As/InP double-heterojunction bipolar transistors (DHBTs) on GaAs substrate are investigated for the first time. The noise figures and associated gains of the device with an emitter size of 5 × 5 μm2 are studied in the frequency range of 2–10 GHz. The variations of minimum noise figure at different collector currents are presented. At 2 GHz, the best minimum noise figure (FMIN) of 2.1 dB with an associated gain (GASS) of 12.7 dB have been achieved at VCE= 1.5 V and IC= 0.3 mA (1.2 kA/cm2). For comparable size and current density, these results show noise performance comparable to those of reported lattice-matched InP HBT at lower frequency (∼2 GHz). © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 306–308, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10303 [ABSTRACT FROM AUTHOR]

In this paper we report, for the first time, the investigation of hetero-interface trapping characteristics in AlGaN/GaN with a high-electron-mobility transistor (HEMT) on a CVD-diamond using the conductance method at different temperatures (25 °C to 200 °C). Fast traps with time constants from 0.16 to 10.01 μs were identified to be the dominating traps at the AlGaN/GaN hetero-interface. The density of the traps (DT) was found to increase with temperature and was attributed to the excitation of deeper traps in the bandgap at elevated temperatures. Finally, temperature-dependent pulsed IDS–VDS measurements were taken to correlate the DT behaviour and current collapse in the device. [ABSTRACT FROM AUTHOR]

The traps in an AlGaN/GaN metal-insulator-silicon-high-electronmobility- transistor on silicon are investigated by analysing the random-telegraph-signal (RTS) noise in the drain current. Two different types of RTS noise due to the traps at the gate-oxide and AlGaN have been observed in this reported work. Through the analysis of the two RTS noises, the presences of the two trap types are verified and the trap locations have also been identified. [ABSTRACT FROM AUTHOR]

The distribution of trap energy (DTE) levels was observed in the energy band gap of buffer GaN by temperature-dependent current transient measurements on AlGaN/GaN HEMTs under fully ON drain-stress (VD[ON]_Stress) conditions. The activation energies (Ea’s) obtained from current transients increase with increasing VD[ON]_Stress. Using a multitrap energy (MTE) model, the applied-VD[ON]_Stress-dependent Ea is attributed to DTE levels in the GaN energy band gap, rather than to discrete single trap energy levels. An effective activation energy (Ea_eff) corresponding to trap energy levels activated by the applied VD[ON]_Stress is thus obtained. This observation is validated with two-dimensional numerical simulations. This study will help device designers develop a “DTE-dependent” emission time constant model that is readily applicable for the reliability modelling of future GaN-based circuits. [ABSTRACT FROM AUTHOR]

We have demonstrated 0.17-µm gate-length In0.17Al0.83N/GaN high-electron-mobility transistors (HEMTs) on Si(111) substrates using a non-gold metal stack (Ta/Si/Ti/Al/Ni/Ta) with a record-low ohmic contact resistance (Rc) of 0.36 Ω mm. This contact resistance is comparable to the conventional gold-based (Ti/Al/Ni/Au) ohmic contact resistance (Rc = 0.33 Ω mm). A non-gold ohmic contact exhibited a smooth surface morphology with a root mean square surface roughness of ∼2.1 nm (scan area of 5 × 5 µm2). The HEMTs exhibited a maximum drain current density of 1110 mA/mm, a maximum extrinsic transconductance of 353 mS/mm, a unity current gain cutoff frequency of 48 GHz, and a maximum oscillation frequency of 66 GHz. These devices exhibited a very small (<8%) drain current collapse for the quiescent biases (Vgs0 = −5 V, Vds0 = 10 V) with a pulse width/period of 200 ns/1 ms. These results demonstrate the feasibility of using a non-gold metal stack as a low Rc ohmic contact for the realization of high-frequency operating InAlN/AlN/GaN HEMTs on Si substrates without using recess etching and regrowth processes. [ABSTRACT FROM AUTHOR]

The impact of low-k dielectric benzocyclobutane (BCB) encapsulation on the electrical performance and structural stability of AlGaN/GaN HEMTs on Si were investigated. After BCB encapsulation, devices exhibited no degradation in their drain current density, extrinsic transconductance and small signal microwave performances. The curing temperature (280 °C) of BCB layer had no influence on the device electrical performances. Compared to devices without BCB encapsulation, the BCB encapsulated devices achieved ∼2 orders of magnitude lower gate- and drain-leakage current. An order of magnitude lower surface leakage current was also observed by BCB encapsulation between the two adjacent mesas. Due to the reduction of leakage currents, ∼2-times increase of OFF-state breakdown voltage was observed. In addition, the 9-µm-thick BCB encapsulation layer also helps to have structurally stable air bridges. This work demonstrates the low-k dielectric BCB as a viable solution for the complete encapsulation of GaN HEMTs and ICs. [ABSTRACT FROM AUTHOR]

The hole-initiated impact ionization multiplication factor M[sub p]-1 and the ionization coefficient α[sub p] in AlGaAs/InGaAs p-n-p heterojunction bipolar transistors (HBTs) are presented. A large discrepancy is observed at low electric field when the measured data from the p-n-p HBTs are compared with those given from avalanche photodiode. The results show that the conventional impact ionization models, based on local electric field, substantially overestimate the hole impact ionization multiplication factor M[sub p]-1. We believe that the hole ionization coefficient in p-n-p HBTs where significant dead space effects occur in the collector space charge region. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]