Osamu Kumagai

Transmission electron microscopic study of the ordered structure in GaInP/GaAs epitaxially grown by metalorganic chemical vapor deposition

GaInP epitaxial crystals grown on (001) GaAs at 660–700 °C by metalorganic chemical vapor deposition are examined by transmission electron microscopy. The computer‐processed image of the high‐resolution electron micrograph clearly reveals a lamellate‐ordered domain structure of two variants of {111} superlattices, which is also investigated using cross‐section and plan‐view dark field electron micrographs. The spikes of well‐defined superspots in the diffraction pattern were found to originate from the shape of the domains. The investigation of GaInP grown with different Zn concentrations showed that the disordering occurs as a result of a decrease in the density rather than the size of the domain.

680-nm band GaInP/AlGaInP tapered stripe laser

A gain‐guiding tapered stripe laser was fabricated using a Ga0.5In0.5P/(Al0.5Ga0.5)0.5In0.5P double heterostructure wafer grown by metalorganic chemical vapor deposition. The laser showed a continuous wave (cw) threshold current of 48 mA, a maximum temperature for cw operation of 81 °C, an aspect ratio of about 2, and an astigmatism near 25 μm. The emission wavelength was 684 nm. Thirty‐two devices have been operating without significant degradation for more than 2000 h at 50 °C with a constant output power of 3 mW.

Fe ion dose dependence of deep levels in Si p+‐n junction

A peak of deep level transient spectroscopy (DLTS) spectrum obtained from a silicon p+‐n junction implanted with iron was investigated and it was found that the energy level and the capture cross section of the trap varied with the iron dose. This is due to a change, with dose, of the concentration ratio of two kinds of traps, a process induced (E3:Ec−0.50 eV) and an iron‐associated center (E2:Ec−0.58 eV), which have nearly the same emission rate and give only a single peak to the DLTS spectrum. The concentration of the E2 trap depended on the iron dose, while that of the E3 trap did not.

Deep Levels Introduced by Iron Implantation in n-type Silicon and Its Application to Switching Devices

A new life time control method in silicon was developed by making use of implantation of iron. By choosing a dose level of iron and anneal temperature, we obtained a nearly temperature independent hole life time in a well controlled manner in n-type silicon. It was found by studying compensating effects only donor centers were introduced by iron implantation. The energy levels and the capture cross sections of these centers were determined by DLTS. Minority carrier life time was analyzed by assuming that the two of these centers were responsible for the recombination, and a fairly good agreement was obtained with life time data. We applied the iron implantation method to gate controlled switches (GCSs) and demonstrated this method was very suitable for controlling the time constant of switching devices.

In‐depth profiles of deep‐trap concentration in Fe‐implanted n‐type silicon

A peak of deep‐level transient‐spectroscopy spectrum obtained from iron‐implanted n‐type silicon was investigated, and it was found that the apparent energy level of the trap varied as the distance from the implanted layer increased. This is due to a change, with the distance, of the concentration ratio of two kinds of traps, an implantation‐induced (E3:Ec −0.50 eV) and an iron‐associated center (E2:Ec −0.58 eV). The E2 trap concentration showed an L‐shaped in‐depth profile. In the sample with a p+‐diffused layer on the surface opposite of the iron‐implanted layer, the in‐depth profile of the E2 trap concentration was U shaped. These in‐depth profiles can be explained in terms of interstitial‐substitutional diffusion of iron atoms.

A High-power Tapered-SAN Laser for an Optical Pick-up

A high-power laser with a tapered stripe structure has been developed and demonstrated to have a small aspect ratio in far field pattern, a small astigmatic distance, and good reliability. The beam divergence in the parallel direction can be controlled by varying the shape of the tapered stripe. This laser makes it possible to building up a compact, low cost optical pick-up for magneto-optical disk drives.

Control of Lifetime in Silicon by Implantation of Iron

The hole lifetime in n-type silicon could be reduced by the implantation of iron in a well-controlled manner. By choosing a suitable dose and annealing temperature, a nearly temperature-independent hole lifetime was obtained. The temperature dependence of the hole lifetime was analyzed by the Shockley-Read-Hall theory, and we found that two types of recombination centers,-that is, a process-induced center and an iron-implanted center,-were responsible for the recombination. The energy level, the capture cross section, and the charge state of these centers were determined by deep-level transient spectroscopy (DLTS) and by compensation effect. We applied the method of iron implantation to fast-switching diodes and gate-controlled switches (GCSs) and demonstrated that iron offered improved high-temperature properties when applied to switching devices.

Application of Laser Diodes to Optical Disk Systems: The History of Laser Diode Development and Mass Production in Three Generations of Optical Disk Systems

Twenty years after Dr. Holonyaks invention, a compact disc (CD) was introduced to the market in 1982. A laser diode is always in the heart of optical storage systems and a variety of other industrial applications. Innovations in laser diode technologies have brought optical storage evolutions from CD to digital versatile disc (DVD) and then Blu-ray disc (BD) every ten years. Since the most important reason for our success in laser development is our choice of metalorganic chemical vapor deposition (MOCVD) for growing these semiconductor alloys, MOCVD equipment, growth conditions, material properties, and phenomena associated with MOCVD and various alloy lasers grown by MOCVD are described in detail. Reviewing the development history would tell us how the laser diode has created a huge market and why recent innovations will predict future applications.

680nm AlGaInP Visible Lasers Grown By MOCVD

A gain-guide tapered stripe laser was fabricated by metalorganic chemical vapor deposition. Improved characteristics, such asoa low threshold current of 48mA, a maximum temperature for continuous wave operation of 81C and an small astigmatic difference of 25pm, have been achieved. Sixteen cdevices have been operating without significant degradation for more than 5000 hours at 50C with a constant output power of 3mW. A high output power of 250mW has also obtained by the broad stripe laser.

DLTS Study of Cr Trap Density in Thermally Converted Semi-Insulating GaAs

Deep traps in Cr-doped semi-insulating GaAs annealed under various arsenic partial pressureswere investigated by DLTS and in-depth profiles of Cr trap density were obtained. The profiles show out-diffusion of Cr traps. Near the surface region, however, the electrically active Cr trap density was about ten times lower than the Cr atomic density.