I. Ladany

Accelerated step‐temperature aging of AlxGa1−xAs heterojunction laser diodes

Double‐heterojunction Al0.3Ga0.7As/Al0.08Ga0.92As lasers (oxide‐striped and Al2O3 facet coated) were subjected to step‐temperature aging from 60 to 100 °C. The change in threshold current and spontaneous output was monitored at 22 °C. The average time required for a 20% pulsed threshold current increases from about 500 h, when operating at 100 °C, to about 5000 h at 70 °C. At 22 °C, the extrapolated time is about 106 h. The time needed for a 50% spontaneous emission reduction is of the same order of magnitude. The resulting ’’activation energies’’ are ∼0.95 eV for laser degradation and ∼1.1 eV for the spontaneous output decrease.

The influence of stripe width on the threshold current of double-heterojunction lasers

Experimental measurements of the threshold current of oxide‐isolated stripe lasers as a function of stripe width and p‐layer resistivity are presented. A calculation of the influence of carrier outdiffusion has been made, including the effect of current leakage beyond the stripe edges. The calculated threshold increase is in substantial agreement with experiment for stripe widths down to about 10 μm. The data also yield an effective diffusion length of ∼7 μm for the lasers studied. Deviations between experimental and calculated thresholds occurring at stripe widths of 4–6 μm are represented by an empirical curve which is compared with previously published calculations of threshold gain.

Lateral mode selection in semiconductor injection lasers

Various methods have been used to control the lateral modes of injection lasers. We report on lateral mode selection in continuous‐wave double‐heterojunction lasers using the differential diffraction losses of different modes at a narrow reflector stripe on one emitting facet. Power output curves and far‐field beam patterns scanned in the lateral (junction) plane are shown both before and after an antireflection coating was deposited on one facet except in a narrow stripe. The stripe defines the mode‐selecting reflective region. Calculations, based on a simple model of DH injection lasers, are made by estimating the magnitude of the effect. Output powers of 12 mW from one facet were obtained.

Meltback and pullover as causes of disturbances in liquid‐phase epitaxial growth of InGaAsP/InP 1.3‐μm laser material

InGaAsP/InP 1.3‐μm laser material grown by liquid‐phase epitaxy occasionally exhibits an anomalous x‐ray diffraction pattern and may also have a high threshold current density. The origin of this effect is shown to be the contamination of the normal p‐type InP cladding layer with Ga and As. A typical composition of this quaternary cladding layer is determined, and secondary‐ion mass‐spectrometry analyses are used to show the contamination is most likely caused by pullover from the previous melt.

Cathodoluminescence of AlxGa1−xAs grown by liquid‐phase epitaxy

Small‐area contrast fluctuations observed in cathodoluminescence‐mode SEM images of thin AlxGa1−xAs layers grown by liquid‐phase epitaxy on GaAs : Cr substrates are attributed to local variations in alloy composition. Quantitative estimates of the composition excursions are obtained from the variations in CL intensity by calibration against compositions known from electron‐probe microanalysis. In a typical sample, the CL variations are shown to correspond to peak‐to‐peak fluctuations of about 1 at.% of Al and occur over irregular regions generally in the range 6–20 μm in diameter.

Growth initiation and cathodoluminescence irregularities in LPE AlGaAs layers

In a previous publication, we described the occurrence of a patchy contrast in cathodoluminescence (CL) images of thin LPE layers of AlGaAs grown on Cr‐doped GaAs substrates. The present paper, a continuation of that work, reports on CL observations of LPE AlGaAs layers grown on Si‐doped GaAs substrates and on freshly grown Sn‐doped LPE layers; in addition, we have examined changes in the CL intensity distribution with layer thickness. It is concluded that the ’’patches’’ are confined to a region near the GaAs‐AlGaAs interface, and that their appearance is associated with the initiation of the AlGaAs epilayer growth.