Shigeharu Matsushita

A high power-added efficiency GaAs power MESFET operating at a very low drain bias for use in L-band medium-power amplifiers

A power MESFET offering a high eta /sub add/ operating at a very low V/sub DD/ has been developed. The MESFET has a buried p-layer and an improved LDD (lightly doped drain) n+ self-aligned structure which include highly electrically activated ion-implanted regions due to rapid thermal-cap annealing using double-layered SiN films deposited by ECR plasma chemical vapor deposition. The device geometries and implantation conditions were optimized to achieve a high V/sub (BR)GDO/ of more than 10 V and a low V/sub K/ of less than 0.5 V, and to minimize the bias dependence of S-parameters. This produced excellent electrical characteristics such as P/sub 0(1dB/)=177 mW (173 mW), eta /sub add/=38.8% (32.6%) at V/sub DD/=3 V (2 V), and I/sub DS/=0.16 A ( approximately 0.4I/sub DSS/) (0.24 A ( approximately 0.6I/sub DSS/)) at 1.9 GHz.<<ETX>>

Diffusion and doping of Si into GaAs from undoped SiOx/SiN film

The diffusion and n‐type doping of Si into GaAs from a novel diffusion source consisting of an undoped SiOx/SiN double‐layered film were achieved by rapid thermal annealing at 860–940 °C. The film properties of the double‐layered films employed as Si diffusion sources are experimentally presented. The characteristics of the Si diffused layers were investigated by secondary ion mass spectrometry, capacitance‐voltage measurement, and the Hall method. The carrier profiles exceeded 2×1018 cm−3 and featured an abrupt diffusion front, while a maximum electron concentration of 6×1018 cm−3 was obtained at 940 °C. The diffused Si profiles were consistent with the SiGa+−VGa− pair diffusion model.

A novel access scheme suppressing disturbance for a cross-point type ferroelectric memory

To resolve the disturbance problem of stored data being destroyed in a cross-point type FeRAM, which has prevented it from being put into practical use, we propose a novel access scheme for read-restore sequence. The unique point of this scheme is two restore sequences that are dynamically changed according to read-out data. Based on this scheme, the reduction of polarization induced by the disturbance is suppressed to be less than 17% after stress iteration of 10/sup 9/ times.

Influence of rapid thermal annealing on modulation doped structures

Abstract We have investigated the influence of high temperature annealing on modulation doped structures of AlGaAs/GaAs, AlGaAs/InGaAs and InAlAs/InGaAs systems grown by molecular beam epitaxy. Hall-measurement reveals reduction in two-dimensional electron gas mobility and almost unchanged sheet density after annealing at 800–880°C for 5 s in each hetero-junction system. The mobility reduction is enhanced with the increase in annealing temperature and with the decrease in thickness of a spacer between a donor layer and a channel layer. This behavior is attributed to diffusion of Si dopants from a donor layer to a spacer layer resulting in an increasing ionized impurity scattering effect. It is found that In contained structures especially an InP-based InAlAs/InGaAs structure, provide both large 2DEG sheet density and excellent thermal stability of the modulation doped structure.

Quantification of Electrical Deactivation by Triply Negative Charged Ga Vacancies in Highly Doped Thin GaAs Layers.

We present for the first time a theoretical approach to electrical deactivation by triply negative charged Ga vacancies (V 3- Ga in highly doped thin n-GaAs layers grown by molecular beam epitaxy, and quantify their deactivation under as-grown and annealed conditions. We also show that thinning of n-GaAs epitaxial layers results in low-level electrical deactivation. This effect is apparently caused by the fact that thinning of the doped layers results in lowering of the Fermi energy in the doped layers, and thereby inhibition of the generation of V 3- Ga acceptors. Furthermore, we deduce from the results of this study the thermal equilibrium concentration of V 3- Ga in intrinsic GaAs. The resulting expression is [V 3- Ga (i)] = 5.37 X 10 31 exp(-4.64eV/k B T) cm -3 .

Excellent Thermally Stable Epitaxial Channel for Implanted Planar-Type Heterojunction Field-Effect Transistors

We demonstrate for the first time that the decrease in the carrier concentration of highly doped GaAs layers caused by annealing is alleviated by thinning the layers. It is also suggested that the decrease is dependent on the Fermi energy in the doped layers. Thermally stable thin Si-doped GaAs channels are formed in implanted planar-type two-mode channel field-effect transistors (P-TMTs). A 0.2-μm device having a GaAs channel 9 nm thick with a doping level of 7 x 10 18 cm -3 exhibits excellent performance, such as a transconductance g m of 450 mS/mm, a current-gain cutoff frequency f T of 72 GHz, and a maximum frequency of oscillation f max of 140 GHz. Furthermore, it is indicated that highly doped thin layers are very effective for improving the DC and microwave performance of P-TMTs.

New Planar Two-Mode Channel Field-Effect Transistor Suitable for L-Band Microwave Monolithic Integrated Circuits with RF Transmission and Reception Blocks Operating at Vdd≤ 2 V

A new planar-type two-mode channel field-effect transistor (P-TMT) for L-band microwave monolithic integrated circuits (MMICs) with RF transmission and reception blocks operating at a very low supplied voltage (V dd ≤ 2 V) for use in the 1.9-GHz-band personal handy phone system (PHS) has been developed. By simply changing the gate width (W g ), P-TMTs with W g = 400 μm and W g = 2600 μm were fabricated for low-noise and high-power applications, respectively. At the drain voltage (V ds ) of 2 V, a minimum noise figure (F min ) of 0.65 dB, an associated gain (G a ) of 17.6 dB at drain current (I ds ) of 3 mA, and a 1 dB gain compression (P o(1 dB) ) of 22.8 dBm at I ds = 300 mA were obtained. Moreover, at V ds = 1.5 V, F min of 0.65 dB, G a of 16.9 dB at I ds = 3 mA, and P o(1 dB) of 20-9 dBm at I ds = 350 mA were obtained

Doping profile control and two‐dimensional electron gas formation by Si diffusion into III‐V compounds

The doping characteristics of Si‐diffused III‐V compounds have been investigated using fully dielectric diffusion sources consisting of undoped SiOx/SiN double‐layered films prepared by plasma‐enhanced chemical‐vapor deposition. It is demonstrated that the rectangular‐shaped carrier concentration profiles resulting from the Si diffusion in GaAs can be controlled by varying the deposition parameters of the SiOx/SiN films, i.e., the N2O flow rate in the SiOx deposition, the SiOx film thickness, and the NH3 flow rate in the SiN deposition. It is explained that the profile variations are determined by the quantity of an excess of Si in the SiOx bottom film and the outdiffusion rate of Ga and/or As from GaAs. Furthermore, the Si diffusion experiments are carried out in AlxGa1−xAs, and the formation of a two‐dimensional electron gas with a Hall mobility of 5060 cm2/V s at 300 K and 97 500 cm2/V s at 77 K is achieved by diffusing Si into an undoped GaAs/Al0.22Ga0.78As heterostructure.