Lattice-matched High Electron Mobility Transistors Research Articles

Effect of Trap Behavior on the Reliability Instability of Metamorphic Buffer in InAlAs/InGaAs MHEMT on GaAs.

Our investigation focused on assessing the influence of the metamorphic buffer in metamorphic high-electron-mobility transistors (MHEMT) that were grown on GaAs substrates. While an MHEMT exhibited elevated off-state current levels, its direct current (DC) and radio frequency (RF) traits were found to be comparable to those of InP-based lattice-matched high-electron-mobility transistors (LM-HEMTs). However, the Pulsed I-V measurement results confirmed the presence of the fast transient charging effect, leading to a more substantial degradation in drain current observed in MHEMT. In addition, through the low-frequency noise characteristics, it was confirmed that the dominant trapping location was located in the bulk site. The slope of the 1/f noise measurement indicated that the primary trapping site was in proximity to the bulk traps. The carrier-number-fluctuation (CNF) model was employed to extract the bulk trap density (Nt). For the LM-HEMTs, the value was at 3.27 × 1016 eV-1·cm-3, while for the MHEMT, it was 3.56 × 1017 eV-1·cm-3.

Quantum mechanics prescriptions for compound-semiconductor transistor technologies

We employ an accurate one-dimensional, self-consistent quantum-mechanical–Poisson solver to derive parameters that enable the Poisson solver to accurately compute charge– or capacitance–voltage curves for use in two-dimensional solvers. We consider metal-oxide-semiconductor field effect transistors (MOSFETs), where we adjust gate work functions and oxide thicknesses and SiGe MOSFETs with spacer layers where we adjust gate work functions and the carrier densities in the spacer layers. For GaAs pHEMTs, InP lattice-matched high electron mobility transistors (HEMTs), SiGe HEMTs, double-heterojunction pHEMTs, AlGaN/GaN HEMTs and delta-doped MESFETs we adjust the Schottky barrier heights to shift pinchoff voltages.

Impact of two-step-recessed gate structure on RF performance of InP-based HEMTs

The RF performance of InP-based lattice-matched high electron mobility transistors (HEMTs) is improved by using a two-step-recess process. 0.07 µm gate HEMTs show a cutoff frequency (fT) of 300 GHz, a value previously achievable only with a gate length of 0.05 µm in the conventional gate structure, and a maximum frequency of oscillation fmax of 400 GHz. The high fT indicates that the effective gate length is successfully suppressed by the two-step-recessed gate structure. Moreover, owing to the selective etching property, this gate recess process provides high uniformity of the threshold voltage and the cutoff frequency of the HEMTs on a 3 in wafer.

Molecular beam epitaxy growth of InP-based lattice-matched high electron mobility transistor structures having a modified quantum-well profile due to Al xGa yIn 1 − x − yAs( x + y = 0.47−8) buffer layer

The quaternary compound, Al x Ga y In 1 − x − y As ( x + y = 0.47−8) lattice-matched to InP substrates was realized as a buffer layer in an InP-based lattice-matched high electron mobility transistors. The band gap energy of this quaternary compound buffer layer was linearly decreased from E g = 1.54 eV for Al 0.48Ga y=0 In 0.52As to E g = 0.82 eV for Al x=0 Ga 0.47In 0.53As by varying Al and Ga mole fraction simultaneously. A self-consistent analysis revealed, one, that this buffer layer modified the quantum-well structure into a triangular-shaped conduction-band profile and, two, the disappearance of the quantum-well in valance-band profile. By forming a triangular-shaped conduction-band quantumwell, carrier wave functions drifted farther apart from the heterointerface, leading to the reduction of ionized impurity scattering. Disappearance of holes in a valance band also contributed to the reduction of the hole and electron recombination scattering. A high electron mobility of 11 338 cm 2/V s with two-dimensional electron gas density of 2.5 × 10 12/cm 2 was achieved at room temperature. The high electron mobility was believed to have resulted from the modified triangular-shape quantum well in which the ionized impurity ion scattering was suppressed. We believe that we have achieved the highest room temperature value of electron mobility time with two-dimensional electron gas concentration that was 2.83 × 10 16/cm 2 to date for InP-based lattice-matched high electron mobility transistors system. PL measurement showed some evidences of a high-quality epitaxial growth.

Pseudomorphic InGaAs high electron mobility transistors

High electron mobility transistors (HEMTs) with single-quantum-well active layers composed of pseudomorphic InGaAs on GaAs and InP substrates have yielded substantial performance enhancements relative to their lattice-matched equivalents. The higher cut-off frequencies possessed by these devices have enabled new applications to be realized in the millimeter wave spectrum which are not feasible with lattice-matched HEMTs. Also, the devices are beginning to displace GaAs field effect transistors in the microwave spectrum as a result of higher gain and power-added efficiency inherent to the pseudomorphic devices. These developments in transistors and parallel developments in other strained layer material systems and devices have been paced by a resurgence in research and development in the materials science and engineering of strained epitaxial layers.

5-100 GHz InP coplanar waveguide MMIC distributed amplifier

A single-stage 5-100-GHz InP MMIC (monolithic microwave integrated circuit) amplifier with an average gain of more than 5.5 dB has been developed. This MMIC distributed amplifier has the highest frequency and bandwidth of operation (5-100 GHz) reported to date for wideband amplifiers. The average associated (not optimized) noise figure of the MMIC amplifier was approximately 5.8 dB measured over 4-40 GHz. The active devices in this seven-section distributed amplifier were 0.1- mu m mushroom gate, InGaAs-InAlAs lattice-matched HEMTs (high electron mobility transistors) on a semi-insulating InP substrate. A coplanar waveguide was the transmission medium for this 100-GHz MMIC with an overall chip dimension of 500 mu m by 860 mu m.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>