Toshio Kikuta

1.3 μm InAsyP1−y/InP strained‐layer quantum well laser diodes grown by metalorganic chemical vapor deposition

We report on the metalorganic chemical vapor deposition (MOCVD) growth of InAsyPl1−y/InP strained layer quantum wells and the successful lasing of novel InAsyP1−y/InP strained layer quantum well laser diodes at 1.3 μm for the first time. Full width at half maximum of room temperature photoluminescence was as narrow as 30.1 meV with a peak wavelength of 1.29 μm. A very low threshold current density of 0.45 kA/cm2 was obtained on broad contact lasers with a cavity length of 900 μm.

1.3 mu m InAs/sub y/P/sub 1/-/sub /y-InP strained-layer quantum-well laser diodes grown by metalorganic chemical vapor deposition

The authors have fabricated 1.3- mu m InAsP-InP separate-confinement-heterostructure (SCH) strained-layer double-quantum-well (SL-DQW) laser diodes (LDs) by metalorganic chemical vapor deposition (MOCVD). A low threshold current density of 410 A/cm/sup 2/ was obtained. The CW threshold current was as low as 1.8 mA at 20 degrees C, and maximum CW operating temperature of 120 degrees C was obtained. These characteristics are almost the same as those of well-designed GaInAsP-InP SL-QW LDs. Further improvement of the characteristics of InAsP-InP LDs is expected by optimizing the device structure. >

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. >

1.48 mu m high-power GaInAsP-InP graded-index separate-confinement-heterostructure multiple-quantum-well laser diodes

High-power 1.48- mu m graded-index separate-confinement-heterostructure multiple-quantum-well laser diodes (GRIN-SCH MQW LDs) have been investigated in terms of the beam divergence, threshold current, and differential quantum efficiency. A calculation predicts that narrow beam divergence perpendicular to the junction plane could be obtained by the use of small number of step quaternary layers with wide bandgap. Experimentally, the threshold current increased due to the small optical confinement, although the beam divergence became small. The full width at half maximum (FWHM) of the far-field pattern in the horizontal direction was 20 degrees and that in the vertical direction was 25 degrees . Output power as high as 208 mW was achieved at a driving current of 1000 mA for a 1-mm-long device. Stable transverse mode operation was confirmed up to the maximum output power. Coupling efficiency of 89% and output power from a single-mode fiber of 185 mW were obtained at 25 degrees C. >

InP single crystal growth with controlled supercooling during the early stage by a modified LEC method

A new liquid encapsulated Czochralski (LEC) technique for InP single crystal growth has been developed. In order to restrain the generation of twin bondaries from the shoulder of InP crystal by the LEC method, at the beginning of InP crystal growth, we tried to produce growth toward the lateral direction until reaching a 2-inch diameter without forming a cone angle (θ = 90°) by controlling the optimum supercooling of the InP melt. As a result, it was found that although isotropic growth could restrain the twin boundary, anisotropic growth was likely to generate a twin boundary at the completion of lateral growth. After isotropic growth, InP single, crystals were obtained reproducibly. That is, ten single crystal ingots of InP were obtained by this method. Furthermore, the etch pit density (EPD) of InP water with a 2-inch diameter was less than 2000 cm-2, except at the edge of the water, by Zn doping ((3.0-4.0) X 1018 cm-3).

AIGaAs/GaAs Heterojunction Bipolar Transistors with C-Doped Base Grown by AP-MOVPE

Abstract C-doped GaAs layers were grown by the atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) method using TMGa and TMAs at low temperature and low V/III ratio. Carbon concentrations up to 7 × 10 19 cm −3 were obtained, and their mobility was higher than for Zn-doped GaAs. Using this C-doped GaAs as the base layer, AlGaAs/GaAs HBTs were fabricated, and current gain up to 50 was demonstrated for the sample with a base layer of 700 A in thickness and 4 × 10 19 cm -3 in concentration. The uniformity across the wafer and the reproducibility of the current gains were considered to be good enough for the use of this epitaxial layers as HBT ICs.

High quality Si-InP bulk crystal growth by horizontal gradient freeze method under controlled phosphorus vapor pressure

Abstract High purity InP was grown by horizontal gradient freeze (HGF) method under controlled phosphorus vapor pressure. The ingot was free from residual In and In inclusion. The carrier concentration of undoped InP ingot was almost in the range of (1.1–4.0)×10 15 cm -3 at 77 K even though a quartz boat was used. Using this technique, Si-InP wafers with a high resistivity over 1.0×10 7 Ω cm were obtained by lower Fe doping (4.0×10 15 cm -3 ). The growth of single crystals using the seeding technique was also tried by direct synthesis. The strict control of the temperature gradient with the CPU system enabled the seeding to be performed reproducibly. A single crystal, 6 cm long, was obtained from the seed end of the ingot, but twin boundaries were generated from the middle of the ingot.

Heavily Zn-doped graded-base AlGaAs/GaAs HBTs grown by MOCVD

Heavily Zn-doped graded-base AlGaAs/GaAs HBTs with base doping concentrations of 3.5*10/sup 19/, 5.5*10/sup 19/, and 8.1*10/sup 19/ cm/sup -3/ were fabricated using metalorganic chemical vapor deposition (MOCVD)-grown epitaxial wafers. The maximum measured current gain was 42 with a base doping concentration of as high as 8.1*10/sup 19/ cm/sup -3/. The current gain decreased drastically from 96 to 42 when doping concentration increased from 3.5*10/sup 19/ to 8.1*10/sup 19 /cm/sup -3/. Assuming that the emitter efficiency is unity, the minority electron lifetime in the base is estimated by the current gain by consideration of drift in the graded base. The dependence of the electron lifetime in the graded base on Zn doping concentration was similar to that in a uniform base. >

MOVPE growth of highly zinc-doped bases for GaAs/AlGaAs heterojunction bipolar transistors

GaAs/AlGaAs HBT epitaxial layers with highly zinc-doped bases have been succesfully fabricated by an atmospheric pressure MOVPE method. By optimizing the growth temperature, a highly doped Zn concentration and an abrupt Zn profile can be achieved at the same time. Current gain over 40 was obtained for a graded base HBT with a high Zn concentration (5×1019 cm-3) and 25×25 μm2 emitter.