Shinichi Nakatsuka

Bio: Shinichi Nakatsuka is an academic researcher from Hitachi. The author has contributed to research in topics: Laser & Laser diode. The author has an hindex of 12, co-authored 79 publications receiving 1138 citations. Previous affiliations of Shinichi Nakatsuka include Ricoh.

GaInNAs: a novel material for long-wavelength semiconductor lasers

Abstract: GaInNAs was proposed and created in 1995 by the authors. It can be grown pseudomorphically on a GaAs substrate and is a light-emitting material having a bandgap energy suitable for long-wavelength laser diodes (1.3-1.55 /spl mu/m and longer wavelengths). By combining GaInNAs with GaAs or other wide-gap materials that can be grown on a GaAs substrate, a type-I band lineup is achieved and, thus, very deep quantum wells can be fabricated, especially in the conduction band. Since the electron overflow from the wells to the barrier layers at high temperatures can he suppressed, the novel material of GaInNAs is very attractive to overcome the poor temperature characteristics of conventional long-wavelength laser diodes used for optical fiber communication systems. GaInNAs with excellent crystallinity was grown by gas-source molecular beam epitaxy in which a nitrogen radical was used as the nitrogen source. GaInNAs was applied in both edge-emitting and vertical-cavity surface-emitting lasers (VCSELs) in the long-wavelength range. In edge-emitting laser diodes, operation under room temperature continuous-wave (CW) conditions with record high temperature performance (T/sub 0/=126 K) was achieved. The optical and physical parameters, such as quantum efficiency and gain constant, are also systematically investigated to confirm the applicability of GaInNAs to laser diodes for optical fiber communications. In a VCSEL, successful lasing action was obtained under room-temperature (RT) CW conditions by photopumping with a low threshold pump intensity and a lasing wavelength of 1.22 /spl mu/m.

Room-Temperature Pulsed Operation of GaInNAs Laser Diodes with Excellent High-Temperature Performance

Abstract: We have successfully operated GaInNAs laser diodes with a pulsed current at room temperature. The lowest threshold current density was about 0.8 kA/cm2, and the lasing wavelength was about 1.2 µ m. Characteristic parameters such as internal quantum efficiency and the gain constant were measured, and excellent high-temperature performance was observed. The characteristic temperature was 127 K in the temperature range from 25 to 85° C.

Room-temperature lasing operation of GaInNAs-GaAs single-quantum-well laser diodes

Abstract: We have succeeded in demonstrating continuous-wave (CW) operation of GaInNAs-GaAs single-quantum-well (SQW) laser diodes at room temperature (RT). The threshold current density was about 1.4 kA/cm/sup 2/, and the operating wavelength was approximately 1.18 /spl mu/m for a broad-stripe geometry. Evenly spaced multiple longitudinal modes were clearly observed in the lasing spectrum. The full-angle-half-power far-field beam divergence measured parallel and perpendicular to the junction plane was 4.5/spl deg/ and 45/spl deg/, respectively. A high characteristic temperature (T/sub 0/) of 126 K under CW operation and a small wavelength shift per ambient temperature change of 0.48 nm//spl deg/C under pulsed operation were obtained. These experimental results indicate the applicability of GaInNAs to long-wavelength laser diodes with excellent high-temperature performance.

Semiconductor light emitting element and its manufacture

Abstract: PROBLEM TO BE SOLVED: To restrict lamination defects and give longer life by forming a defect restricting layer by one atomic layer or more, having a group II element and a group V element at the interface between a III-V compound semiconductor substrate and a II-VI compound semiconductor crystal. SOLUTION: At the interface between a III-V compound semiconductor substrate 11 and II-VI semiconductor crystals 12 to 20, a defect restricting layer 12 crystallized in a group II element and a group V element is formed. Here, as the group II element, it is desired to be either Zn, Cd, Be or Mg, and as the V group element, it is desired to be one among N, P, As and Sb. The II-VI compound semiconductor crystals 12 to 22 produced on the defect restricting layer 12 are ready to form a secondary growth from an early stage of growth, and the occurrence of lamination defect can be restricted. This defect restricting layer 12 is formed by simultaneous or alternating supply of the raw material of group II element and the raw material of group V element. At this time, it is desirable that the top surface of the III-V semiconductor compound substrate 11 become a stabilized surface or an excessive surface of the group V element.

High‐power operation of index‐guided visible GaAs/GaAlAs multiquantum well lasers

Abstract: Stable transverse mode operation has been realized for the first time in visible (780 nm) multiquantum well lasers composed of seven 3‐nm‐thick GaAs wells separated by six 5‐nm‐thick Ga0.8Al0.2As barriers grown by metalorganic chemical vapor deposition. A self‐aligned structure with a built‐in optical waveguide to stabilize the transverse mode is fabricated by a two‐step epitaxial technique. Low threshold current (35 mA), high output power (up to 40 mW) in the fundamental transverse mode, and a very low degradation rate at 70 °C have been confirmed.

Gan : processing, defects, and devices

Abstract: The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

InGaAsN solar cells with 1.0 eV band gap, lattice matched to GaAs

Abstract: The design, growth by metal-organic chemical vapor deposition, and processing of an In{sub 0.07}Ga{sub 0.93}As{sub 0.98}N{sub 0.02} solar Al, with 1.0 ev bandgap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6-0.8 pm, and solar cell internal quantum efficiencies > 70% arc obwined. Optical studies indicate that defects or impurities, from InGAsN doping and nitrogen incorporation, limit solar cell performance.

GaInNAs: a novel material for long-wavelength semiconductor lasers

Abstract: GaInNAs was proposed and created in 1995 by the authors. It can be grown pseudomorphically on a GaAs substrate and is a light-emitting material having a bandgap energy suitable for long-wavelength laser diodes (1.3-1.55 /spl mu/m and longer wavelengths). By combining GaInNAs with GaAs or other wide-gap materials that can be grown on a GaAs substrate, a type-I band lineup is achieved and, thus, very deep quantum wells can be fabricated, especially in the conduction band. Since the electron overflow from the wells to the barrier layers at high temperatures can he suppressed, the novel material of GaInNAs is very attractive to overcome the poor temperature characteristics of conventional long-wavelength laser diodes used for optical fiber communication systems. GaInNAs with excellent crystallinity was grown by gas-source molecular beam epitaxy in which a nitrogen radical was used as the nitrogen source. GaInNAs was applied in both edge-emitting and vertical-cavity surface-emitting lasers (VCSELs) in the long-wavelength range. In edge-emitting laser diodes, operation under room temperature continuous-wave (CW) conditions with record high temperature performance (T/sub 0/=126 K) was achieved. The optical and physical parameters, such as quantum efficiency and gain constant, are also systematically investigated to confirm the applicability of GaInNAs to laser diodes for optical fiber communications. In a VCSEL, successful lasing action was obtained under room-temperature (RT) CW conditions by photopumping with a low threshold pump intensity and a lasing wavelength of 1.22 /spl mu/m.

Fabrication and performance of GaN electronic devices

Abstract: GaN and related materials (especially AlGaN) have recently attracted a lot of interest for applications in high power electronics capable of operation at elevated temperatures. Although the growth and processing technology for SiC, the other viable wide bandgap semiconductor material, is more mature, the AlGaInN system offers numerous advantages. These include wider bandgaps, good transport properties, the availability of heterostructures (particularly AlGaN/GaN), the experience base gained by the commercialization of GaN-based laser and light-emitting diodes and the existence of a high growth rate epitaxial method (hydride vapor phase epitaxy) for producing very thick layers or even quasi-substrates. These attributes have led to rapid progress in the realization of a broad range of GaN electronic devices, including heterostructure field effect transistors (HFETs), Schottky and p–i–n rectifiers, heterojunction bipolar transistors (HBTs), bipolar junction transistors (BJTs) and metal-oxide semiconductor field effect transistors (MOSFETs). This review focuses on the development of fabrication processes for these devices and the current state-of-the-art in device performance, for all of these structures. We also detail areas where more work is needed, such as reducing defect densities and purity of epitaxial layers, the need for substrates and improved oxides and insulators, improved p-type doping and contacts and an understanding of the basic growth mechanisms.

Lid assembly for a processing system to facilitate sequential deposition techniques

Abstract: A lid assembly for a semiconductor processing system is provided. The lid assembly generally includes a lid having first and second opposed surfaces, a plurality of controllable flow channels extending from the first and second opposed surfaces and a gas control system disposed on the first surface and operably opening and closing the channels. The gas control system includes a gas manifold disposed on the lid, at least one valve coupled to the gas manifold and adapted to control a flow through one of the flow channels, a reservoir fluidly connected to the gas manifold, and a precursor source fluidly connected to the reservoir.