Taibun Kamejima

A GaAs-AlxGa1-xAs Double Heterostructure Planar Stripe Laser

A stripe laser structure called a planar stripe was developed. The edge blurring of the current path is improved by the fact that the current spreads only in the thin p-AlxGa1-xAs layer with relatively high resistance. The planar stripe laser has a small threshold current resulting from the small current spreading effect and a good thermal contact. It also shows finely controlled transverse modes, compared with a usual contact stripe laser, and relatively high external differential quantum efficiency. The threshold current density is comparable to that of the proton bombarded stripe laser. The transverse mode shows an approximate Hermite-Gaussian distribution.

Injection-Enhanced Dislocation Glide under Uniaxial Stress in GaAs–(GaAl)As Double Heterostructure Laser

By applying uniaxial stresses of the order of 108–9 dyn/cm2 to (GaAs–(GaAl)As DH lasers in addition to the forward bias current, the development of straight dark lines is observed in the electron beam induced junction current mode using an SEM. They are identified by a TEM as glide dislocations of the /{111} slip system that reflect the resolved shear stress on the slip planes. It is noted that, when no carriers are injected, these dislocations can scarcely be observed in the specimen with an external uniaxial stress. This fact suggests that the enhancement effect of carrier injection on the dislocation glide motion. It is also observed that once drak lines are introduced in the active layer, the dark lines propagate from these drak lines, indicating that the process-induced internal stresses can give rise to the generation of the dark lines.

Nature of 〈110〉 dark‐line defects in degraded (GaAl)As‐GaAs double‐heterostructure lasers

The 〈100〉 dark‐line defects (DLD’s) in the degraded (GaAl)As‐GaAs double‐heterostructure lasers are studied by transmission electron microscopy. Two types of 〈110〉 DLD’s are observed; one is associated with 〈110〉 straight dislocations and the other with dislocation networks developing from the mirror surface. The former type of the 〈110〉 DLD’s is found to be formed by dislocation glide motion. The development of the 〈100〉 dislocation dipole from the 〈110〉 dislocation is also observed, indicating that the 〈110〉 dislocation is a source of the 〈100〉 dislocation dipole.

High optical power density emission from a ’’window‐stripe’’ AlGaAs double‐heterostructure laser

Extremely high optical power density emission (107 W/cm2) was achieved with a new Zn‐diffused ’’window‐stripe’’ laser by eliminating the restriction of the catastrophic optical mirror damage (COMD). The maximum available optical power was at least one order of magnitude higher than the COMD threshold in conventional structures. Furthermore, gradual degradation due to the mirror oxidation has been reduced significantly under cw operation.

Lattice defect structure of degraded InGaAsP‐InP double‐heterostructure lasers

Lattice defect structure of degraded InGaAsP lasers has been investigated by scanning and transmission electron microscopy. It is found that although dislocation climb motion in InGaAsP lasers is slow, slip dislocations parallel to the stripe cause rapid degradation of the lasers.

CW Optical Power from (Al・Ga)As Double Heterostructure Lasers

CW optical output power was investigated in (AlGa)As double heterostructure lasers. An analysis on CW optical power is presented, and parameters related to device characteristics and heat-sinking are analyzed in order to obtain laser operation with high CW optical power. 20–30 mW CW optical power was obtained routinely from each mirror of lasers with a 15 µm wide stripe and a 250 µm long cavity at a typical operating current of 200 mA. Lasers with a Si heat sink can deliver comparably high CW optical power under proper choice of design parameters. Several lasers delivered 85 mW in CW with a Si heat sink from each mirror at 310 mA, before the catastrophic optical mirror damage occurred. Conditions for long life operation are also discussed.

Catastrophic Optical Damage Generation Mechanism in (AlGa)As DH Lasers

Under high optical power operation, (AlGa)As DH lasers suffer from catastrophic optical damage (COD). When the COD occurs dark line defects are observed in the bulk crystal, as well as in mirror surface damage. The COD generation mechanism is clarified by TEM observation of the defects associated with the COD and by investigation on transient behaviors of lasing light excited by one-shot-pulse. It is confirmed that such defects are generated by local overheating up to the melting point of GaAs due to the thermal positive feed back and following transfer of molten zone.

Rapid degradation of InGaAsP/InP double heterostructure lasers due to 〈110〉 dark line defect formation

Rapid degradation has been observed for InGaAsP/InP double heterostructure lasers. It has been found that the rapid degradation is due to 〈110〉 dark line defects generated parallel to the stripe and its occurrence depends on the thickness of the InGaAsP contact layer. It has been shown that formation of a InGaAsP contact layer of more than 0.5‐μm thickness is necessary in order to realize high reliability of the lasers.