Masahiro Kito

Enhanced relaxation oscillation frequency of 1.3 /spl mu/m strained-layer multiquantum well lasers

Dependence of relaxation oscillation frequency (f/sub r/) on the bandgap wavelength of InGaAsP barrier layers (/spl lambda//sub g//sup b/) and number of quantum wells (N/sub w/) were investigated for the first time, for 1.3 /spl mu/m InGaAsP/InGaAsP compressively strained multiquantum well (MQW) lasers. 1.3 times higher f/sub r/ was confirmed for strained-layer MQW lasers with large N/sub w/ (N/sub w//spl ges/7) and wide bandgap barrier layers (/spl lambda//sub g//sup b/=1.05 /spl mu/m) at the same injection level, compared with unstrained MQW lasers having the same well thicknesses and the same emitting wavelength. This enhancement mainly results from increased differential gain due to strain effects separated from the quantum-size effect.<<ETX>>

Control of double diffusion front unintentionally penetrated from a Zn doped InP layer during metalorganic vapor phase epitaxy

Unintentional Zn diffusion during metalorganic vapor phase epitaxy causes serious damages in semiconductor devices. In this work, profiles of unintentionally diffused Zn atoms from a p-InP layer to the adjoining InP substrate during growth of the p-InP layer are measured by secondary ion mass spectrometry. Zn diffusion profiles with a double diffusion front, which is composed of a shallow front with high Zn concentration and a deep front with low Zn concentration, are investigated as an approach to controlling unintentional diffusion. Diffusion depth of each front is controlled in proportion to Zn dosage, which is proposed as a value calculated as Zn concentration without regard to saturation limit. The diffusion depth for the growth time of 60 min increases in proportion to the Zn dosage as the slope of 0.16 μm/1018 cm−3 for the shallow front and that of 0.32 μm/1018 cm−3 for the deep front at a growth temperature of 600 °C. The deep front expands two times faster than the shallow front, which is normall...

New structure by selective regrowth in multi-quantum well laser diodes performed by low pressure metalorganic vapor phase epitaxy

Abstract InGaAsP/InP multi-quantum well (MQW) planar buried hetero-structure (PBH) lasers which are grown entirely by metalorganic vapor phase epitaxy (MOVPE) on n-InP substrates are demonstrated. Two types of lasers, which are different in ridge shape (reentrant or non-reentrant), are investigated in respect of regrowth structure and damage at the regrowth interface. A new regrown structure constructed of a uniformly thick n-InP current-blocking layer formed on a reentrant ridge stripe is demonstrated for the first time. This structure is expected to be effective to suppress leakage current in laser operation. Furthermore, it is found that threshold current and reliability are strongly dependent on regrowth conditions. High quality regrowth interfaces are realized by optimizing regrowth thermal procedure and hole concentration of p-InP current-blocking layer. Stable laser characteristics in accelerated aging tests have been confirmed in both types of lasers.

Anomalous temperature dependence of PL characteristics in ordered InGaAsP strained layer multi-quantum well structure

Clarification of anomalous photoluminescence (PL) characteristics for InGaAsP compressively strained layer multi-quantum well (SL-MQW) structures is studied to realize highly strained SL-MQW lasers with a large number of well layers. PL characteristics such as an increase in PL linewidth and a small temperature dependence of the PL peak wavelength are observed in the SL-MQW structures in which a structure of CuPt-type atomic ordering is observed. Elimination of the ordered structure as well as reduction of the PL linewidth have been confirmed with increasing growth temperature. Although formation of an interfacial undulation (lateral modulation) between SL-MQW layers is also suppressed by the increase in growth temperature, the formation has ultimately limited the maximum strain in SL-MQW. We suggest that the anomalous PL characteristics result from generation of ordering, dominant when the growth temperature is lower, as well as from interfacial undulation, dominant in highly strained SL-MQW when the growth temperature is increased.

Analysis of the second- and third-order intermodulation distortion in DFB lasers including dynamic spatial hole burning effect

Analysis of second and third order intermodulation distortion characteristics of semiconductor DFB lasers is, for the first time, performed, including dynamic longitudinal spatial hole burning (LSHB) effect. We have shown theoretically that the third order intermodulation distortion can be lower than the calculated curve without LSHB effect, which is confirmed with experiments.<<ETX>>

151-channel AM-FDM transmission using 1.3 /spl mu/m strained-layer MQW-DFB laser with high optical output power operation

1.3 /spl mu/m strained-layer multi-quantum well distributed-feedback (SL-MQW-DFB) lasers with low distortion characteristics over wide frequency range even at high optical output power operation have been successfully fabricated. This is achieved by both the high relaxation oscillation frequency characteristics of the SL-MQW active structure and the suppression of non-radiative current in the relatively long laser cavity. By using the laser as a light source for CATV transmission system, high quality AM-FDM transmissions with the largest channel capacity (151ch) have been demonstrated.<<ETX>>

High characteristic temperature 1.48 /spl mu/m strained-layer MQW laser diode with wide bandgap barrier layers

In order to realize high temperature operation of a 1.48 /spl mu/m high power multi-quantum well laser diode, the carrier overflow from the well layers at high temperature should be reduced. This paper shows that utilization of wide bandgap barrier layers in the multi-quantum well structure is effective for this purpose. A highest characteristic temperature of 75 K is achieved.<<ETX>>

1.3 /spl mu/m strained-layer MQW-DFB laser with low noise and low distortion characteristics for 100-channel CATV transmission

1.3 /spl mu/m strained-layer MQW-DFB lasers with large differential gain have been successfully fabricated. The lasers exhibit low distortion and low noise characteristics over wide frequency range even under low bias-current level. These characteristics result from largely improved dependence of relaxation oscillation frequency (f/sub r/) on injection current, due to strain effects. By using the laser as a signal source in CATV systems, high quality AM-FDM transmissions with largest recorded channel capacity (100 ch) have been demonstrated under an extremely low bias-current of 17 mA above threshold current.<<ETX>>