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We propose a novel modulated‐layer‐thickness multiquantum‐barrier (MQB) structure, or chirped MQB. The chirped MQB has a larger potential increase (240 meV) against overflowing electrons than the uniform MQB by almost 100 meV. It also has a broader optimum well thickness width of 1.9 nm while the uniform MQB has only 0.5 nm optimum width. This indicates that the chirped MQB would work more effectively even under the layer thickness fluctuation caused by step bunching, etc.

Accelerated aging tests were carried out under constant current conditions at an ambient temperature range of 100–150 °C for 670 nm band AlGaInP visible laser diodes. A degradation rate activation energy of 0.8 eV and an extrapolated lifetime of 106 h at 50 °C has been obtained. It is reported for the first time that lasing wavelength shifts of up to 20 nm to shorter wavelengths accompanied the threshold current increase. This is attributed to disordering of the natural superlattice in the GaInP active layer.

We show that the low catastrophic optical damage power density observed for AlGaInP laser diodes (LDs) (1/2 to 1/2.9 that of AlGaAs LDs) is mainly attributable to the high thermal resistivities of the materials (5.5 times higher than for AlGaAs LDs) by using a thermal runaway model calculation.

Sputter‐deposited SiO2 films on (AlGa)As DH laser facets were found by chemical erosion tests and Auger spectroscopy to have strong adhesion and an abrupt film‐facet interface profile. Half‐wave coatings by sputtering allowed stable long‐term operation of lasers over several thousand hours at 10–20‐mW (0.7–1.2 mW/μm) power levels at room temperature, almost without change from the initial value of threshold current and optical power.

The facet deterioration of (AlGa)As DH lasers by aging was analyzed by Auger electron spectroscopy in combination with Ar sputter etching. It was found that oxide was formed on the laser facet during cw operation, and the oxidation degraded lasers not only in long‐term operation but also even at an early stage of operation.

The sputter‐deposited SiO2/GaAs interface has been studied by Auger sputter profiling. An interfacial layer is formed even at about 300 °C whenever SiO2 is deposited on the air‐cleaved GaAs surface. On the other hand, when GaAs is cleaved in the sputtering chamber just prior to SiO2 deposition, an interfacial layer is not formed even after annealing at 600 °C, and furthermore the interface is abrupt. Interfacial layer formation is attributed to the existance of thin natural oxide on the GaAs surface.