Akira Iketani

980-nm aluminum-free InGaAs/InGaAsP/InGaP GRIN-SCH SL-QW lasers

The design of 980-nm InGaAs/InGaAsP/InGaP GRIN-SCH lasers with aluminium-free GaAs-based materials is discussed. The first approach was successful MOCVD growth of InGaAsP alloy lattice matched to GaAs. It was found that an immiscible region existed, as determined by photoluminescence measurements. The main approach was to introduce the graded bandgap structure consisting of InGaAsP layers lattice matched to GaAs into GaAs/InGaP interfaces. The graded structure suppresses the heterojunction spikes, especially of the valence band at these interfaces. As a result, series resistance of GRIN-SCH lasers with the graded bandgap structure was reduced compared with simple SCH lasers with abrupt bandgap interfaces due to improved hole injection. Furthermore, the optimum graded structures for optical confinement region were investigated to improve the carrier injection efficiency, especially electron injection efficiency into a single quantum well active layer. Also, this graded bandgap structure formed the graded refractive index profile in an active region, which is the so-called GRIN-SCH waveguide. The GRIN-SCH profile could be controlled to narrow the transverse beam divergence for high coupling efficiency into a single-mode fiber and to reduce the optical power density at facets for high reliability. Finally the results of a life-test of GRIN-SCH lasers was shown, and the lifetime of GRIN-SCH lasers with immiscible InGaAsP layers was discussed. >

InGaAs/InP double‐heterojunction bipolar transistors with step graded InGaAsP between InGaAs base and InP collector grown by metalorganic chemical vapor deposition

We have fabricated InGaAs/InP double‐heterojunction bipolar transistors (DHBTs) grown by metalorganic chemical vapor deposition (MOCVD). By inserting step graded InGaAsP layers between p+‐InGaAs base and n−‐InP collector, the current gain of DHBTs with the graded layers was about twice as large as that without the graded layers, and the dependence of collector current on collector/emitter voltage was smaller than that without graded layers. The current gain was measured up to 2300 with 25×25 μm2 emitter area at a collector current density of 1×104 A/cm2.

0.98 mu m InGaAs-InGaAsP-InGaP GRIN-SCH SL-SQW lasers for coupling high optical power into single-mode fiber

A CW optical power of 75 mW coupled into a single-mode fiber (SMF) at a driving current of 200 mA was achieved by InGaAs-InGaAsP-InGaP graded-index separate-confinement-heterostructure strained-layer single-quantum-well (GRIN-SCH Sl-SQW) ridge waveguide lasers emitting at 0.98 mu m. The GRIN-SCH profile was optimized to minimize the series resistance due to spikes at GaAs-InGaP heterointerfaces. Highly efficient coupling into a SMF with cutoff wavelength of 0.88 mu m by precisely controlling the ridge mesa width (around 2 mu m) and reducing the aspect ratio of the far-field pattern to 1.9. As a result, 0.98- mu m InGaP cladding lasers show performance comparable to the conventional AlGaAs cladding lasers. >

Emitter Material Comparison between InGaP and InGaAsP in GaAs-Based Heterojunction Bipolar Transistors

In0.49Ga0.51P ( Eg=1.87 eV)/GaAs and In0.38Ga0.62As0.22P0.78 ( Eg=1.77 eV)/GaAs Npn heterojunction bipolar transistors (HBTs) were fabricated. In devices with 110 µm×110 µm emitter areas, the curtent gains of both devices were the same value of 14 at a collector current density of 700 A/cm2. By contrast, the turn-on voltage of InGaAsP/GaAs HBTs was 0.01 V smaller than that of InGaP/GaAs HBTs, which indicated that the conduction band discontinuity of the InGaP/InGaAsP heterojunction was much smaller than the valence band discontinuity.

First fabrication of continuously graded InGaAsP on GaAs for 0.98/spl mu/m lasers

InGaAs/GaAs/InGaAsP continuously graded index separate confinement heterostructure (GRIN-SCH) lasers were fabricated by metal organic chemical vapor deposition (MOCVD) for the first time. Transmission electron microscope observation and secondary ion mass spectroscopy measurement show that the continuously graded InGaAsP layers were grown excellently. A very high characteristic temperature of 307K was obtained on the ridge waveguide lasers. Very stable and narrow far field patterns were obtained. The coupling to a single mode fiber was performed with high coupling efficiency of 60%, and output power as high as 78mW was achieved.<<ETX>>

InGaAs/InP double-heterojunction bipolar transistors with graded-InGaAsP between InGaAs base and InP collector grown by metal organic chemical vapor deposition

The fabrication of InGaAs/InP double-heterojunction bipolar transistors (D-HBTs) grown by metal organic chemical vapor deposition (MOCVD) is described. With graded-InGaAsP layers inserted between the p/sup +/ InGaAs base and n/sup -/ InP collector, the current gain of D-HBTs with graded layers was found to be about twice as large as that of D-HBTs without graded layers, and the dependence of collector current on collector/emitter voltage was smaller than without graded layers. The current gain was measured up to 2300 with 25*25 mu m/sup 2/ emitter area at a collector current density of 1*10/sup 4/ A/cm/sup 2/.<<ETX>>