Emi Fujii

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.

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.