E. Mizuki

Molecular‐beam epitaxial growth of InAs/GaAs superlattices on GaAs substrates and its application to a superlattice channel modulation‐doped field‐effect transistor

The molecular‐beam epitaxial growth conditions for (InAs)m(GaAs)n short period superlattices (SPSs) on GaAs substrates have been optimized by monitoring reflection high‐energy electron diffraction (RHEED) intensity oscillations. The RHEED oscillation measurements enable understanding InAs growth behavior on a 7% lattice‐mismatch GaAs substrate. Within one monolayer InAs deposition with lower than 560 °C growth temperature can give high SPS crystalline quality. The SPS periodic structure and the monolayer InAs formation, embedded in GaAs layers, have been confirmed by x‐ray diffraction and transmission electron microscopy measurements. The obtained thickness controllability for the SPSs is less than±6% for InAs and ±3% for GaAs. The electron Hall mobilities for modulation‐doped structures having an (InAs)1(GaAs)n SPS as an electron channel, whose layer index of n varied from 3 to 6, have been compared with those with a pseudomorphic InGaAs random alloy channel which has the equivalent In composition. The S...

High performance 60-GHz coplanar MMIC LNA using InP heterojunction FETs with AlAs/InAs superlattice layer

We describe a 60-GHz coplanar MMIC low-noise amplifier (LNA) using 0.1 /spl mu/m-gate-length InP heterojunction FETs (HJFETs). An optimum gate width of 80 /spl mu/m was determined for the first stage FET by using a small signal model including accurate scaling of the gate resistance. On-wafer noise measurements demonstrated a noise figure of 2.2 dB and a gain of 22.8 dB at 60 GHz.

Electrical properties of InAlAs/InGaAs modulation doped structure after SiN passivated annealing

The effect of thermal annealing on the InAlAs/InGaAs modulation-doped structure, passivated with a SiN film, was investigated. In contrast to the capless sample, the passivated modulation-doped sample exhibited negligible degradation in the two-dimensional electron gas concentration (NS) after annealing at 280 °C, indicating that SiN is an efficient passivation material to ensure good thermal stability for the InAlAs/InGaAs modulation-doped structure. In addition, partial recovery in NS was found by annealing the SiN-passivated sample that had experienced serious NS degradation. A series of secondary ion mass spectroscopy (SIMS) measurements and Hall effect measurements revealed that the recovery of NS is associated with the discharge of fluorine atoms from the Si-doped n-type InAlAs layer.

Striped channel field effect transistors with a modulation doped structure

The authors report the fabrication and performance of the striped channel field effect transistor, which consists of a multiple number of narrow channels fabricated on a modulation-doped heterostructure. The two-dimensional squeezing of the conducting channel by applying gate voltage has been confirmed from the channel width dependence of the drain current. By reducing the channel width of the fabricated 0.25- mu m-gate-length striped channel devices, the authors have observed an enhancement in transconductance as well as improved high-frequency performances. Furthermore, more-than-three-times improvement in the maximum transconductance has been obtained when the device is cooled to 77 K. These results are interpreted based on the improved charge controllability due to the channel squeezing effect as well as on the excellent electron transport properties of ultrafine channels.<<ETX>>

Fluorine diffusion and accumulation in Si step-doped InAlAs layers

The quantitative relation between fluorine (F) accumulation and Si donor concentration in n-InAlAs layers on InP substrate was investigated for several kinds of step-doped InAlAs samples using secondary ion mass spectroscopy. From the depth profile of F and Si donors in a periodic i-/n-InAlAs sample, we found that F accumulates only in n-InAlAs layers, passing through i-InAlAs layers. We also found that the amount of F accumulation in an n-InAlAs layer depends on the Si doping concentration. The experimental results can be explained by considering two states of F. In one state, F is bound to a Si donor and immobile, and in the other it is free and can diffuse.

0.2 mu m T-shaped gate 2DEGFETs with an (InAs) (GaAs) short period superlattice channel on a GaAs substrate

(InAs)/sub 1/(GaAs)/sub n/ short-period superlattice (SPS) channel 2DEGFETs with 0.2 mu m T-shaped gates have been successfully fabricated, and DC and RF performances of the superlattice channel devices have been investigated. Compared to conventional InGaAs alloy channel devices, excellent results in both DC and RF characteristics have been obtained for the SPS channel devices. Higher cut-off frequencies and superior, noise performances of 0.55 dB with an associated gain of 11.26 dB at 12 GHz have been shown. The improved device performances can be explained based on superior electron transport due to the anisotropy of the effective mass of electrons in the SPS channel. These results indicate the great potential of SPS channel structures for high-frequency low-noise device applications.<<ETX>>

V-band MMIC LNA using superlattice-inserted InP heterojunction FETs

This paper presents a V-band MMIC low-noise amplifier (LNA) using InP-based heterojunction FETs (HJFETs). While the HJFET utilizes an AlAs/InAs superlattice as well as non-alloyed ohmic contacts for improved reliability, we show that with appropriate epitaxial layer design these device structures do not lead to increase in the source resistance. The three-stage coplanar waveguide circuit design demonstrated a state-of-the-art noise figure of 2.0 dB with 22.1 dB gain at 60 GHz.

Fluorine diffusion in step-doped InAlAs layers on InP substrate

The quantitative relation between fluorine (F) accumulation and Si donor concentration in n-InAlAs layers on InP substrate was investigated for several kinds of step-doped InAlAs samples using secondary ion mass spectroscopy. From the depth profile of F and Si donor in a periodic i-/n-InAlAs sample, we found that F accumulates only in n-InAlAs layers, passing through i-InAlAs layers. Also, we found that the amount of F accumulation in an n-InAlAs layer depends on the Si doping concentration. The experimental results can be explained by considering two states of F. In one state, F is bound to a Si donor and immobile, and in the other it is free and can diffuse.

InP-based heterojunction FET processing for high-reliability millimeter-wave applications

Describes a novel InP-based FET processing technology for high-reliability microwave applications. High performance InAlAs/InGaAs heterojunction FETs (HJFETs) were fabricated using completely molybdenum-based electrode technology (COMET). The fabricated 1 /spl mu/m gate-length COMET-HJFET exhibited excellent DC and RF performance, including a transconductance of 470 mS/mm and a current gain cutoff frequency of 40 GHz. High temperature DC bias tests performed on the COMET device demonstrated improved reliability compared to that for the conventional InP-based HJFET. The superior reliability of the developed COMET-HJFET is attributed to the reduced interdiffusion between metals of the electrodes and semiconductors by introducing a refractory metal of Mo as a barrier metal.

Novel InAlAs/InGaAs heterojunction FETs with modulated indium composition channel and AlAs/InAs superlattice barrier layer

Novel InAlAs/InGaAs heterojunction FETs (HJFETs) with modulated indium composition channels, named CCMTs (Channel Composition Modulated Transistors), have been successfully fabricated, in which an InAs channel is sandwiched by In/sub 0.53/Ga/sub 0.47/As/In/sub 0.8/Ga/sub 0.2/As sub-channels. The channel structure is designed to improve electron transport and electron confinement by increase effective indium content in consideration of channel electron distribution. The fabricated devices also employ an AlAs/InAs superlattice as a barrier layer against impurity contamination for high thermal stability. A 0.2 /spl mu/m T-shaped gate device exhibits gm of 1370 mS/mm, and Ft of 180 GHz at a low drain bias of 1.0 V. In high temperature and DC life test conducted at more than 230/spl deg/C, the devices exhibited less than 3% degradation after 100 hrs, which shows the developed CCMTs with AlAs/InAs superlattice insertion technology can offer high-performance and highly-reliable InP-based HJFETs for various microwave and millimeter-wave applications.