Abstract

ZnSe-based quantum well (QW) heterostructures are promising for vertical cavity lasers, optical switches, modulators, high density optical memory systems, full colour display panels. The ZnSe/ZnMgSSe/ZnMgSSe separate confined heterostructures (SCH) with single and multiple quantum wells (SQW, MQW) examined in this work were grown on GaAs substrates in a low pressure MOVPE reactor at a total pressure of 400 hPa and a growth temperature of 330°C, using dimethylzinc triethylamine adduct (DMZn(TEN)), ditertiarybutylselenium (DTBSe), ditertiarybutylsulphur (DTBS) and bismethylcyclopentadienylmagnesium ((MeCp)₂Mg) as precursors. Optical properties of the structures were investigated over the temperature range T=78-650 K under the pulse N₂ laser excitation (λ=337.1 nm, τ=8 ns, f=l kHz). The laser action was achieved up to T=577 K (SCH-SQW) and up to T=612 K (SCH-MQ). The laser pulse energy at T=300 K was about 5 nJ. The far field pattern consisted of an oval spot with the divergence (θ/2)_‖ = 14° in the sample plane and (θ/2)_⊥=26° in the perpendicular plane. Fig. 1 shows the laser threshold as a function of temperature and the emission spectra near the threshold at T=500 K (inset). It was shown, using photoluminescence measurements, that the SCHs are stable up to T=500 K. Heating the samples at T=500-650 K leads to a slow (without the N₂ laser beam) or to a fast (with the N₂ laser beam, I_exc> 100 kW/ cm²) degradation. It has been found experimentally that irradiation of the structures with the N₂ laser beam (50-150 kW/cm²) in a temperature range of 400 500 K improves the structure properties and results in a significant increase of the stimulated emission output (Fig. 2) and in a laser threshold reduction.

© 1998 IEEE