摘要:

A horizontal furnace system has been developed for growth by liquid-phase epitaxy of multilayer laser structures consisting of InP and (Ga, In) (As, P) incorporating a number of novel features. Double heterostructure lasers emitting at l.3μm with threshold current densities as low as 900 A/cm2have been made. Measurements of the far-field beam angles have allowed the dielectric constant step between the active quaternary and passive layers for lasers emitting at both 1.15 μm and 1.3μm (im, to be deduced. Oxide-insulated stripe-geometry c.w. lasers, operating in a single longitudinal mode, have been made with threshold currents down to 180 mA

DOI:10.1049/ij-ssed.1979.0035

出版商:IEE    

年代:1979

数据来源: IET

摘要:

This paper describes the growth and characterisation of double heterostructure multilayers of GalnAsP/InP for the fabrication of laser diodes emitting near 1-3 μm. A single-phase growth technique has been employed enabling good uniformity, lattice match and wavelength control. The contact resistance profiling technique has been extensively used in the establishment of a growth procedure which effectively suppresses the diffusion of zinc from the heavily doped capping layer. Lasers fabricated from the material have shown good reproducibility, with pulsed room-temperature thresholds as low as 140 mA for 10 μm wide oxide stripe devices.

DOI:10.1049/ij-ssed.1979.0036

出版商:IEE    

年代:1979

数据来源: IET

摘要:

GalnAsP/InP double-heterostructure lasers were grown by liquid-phase epitaxy on (100) InP substrates for the wavelength region around 1.3μm. The preparation and the properties of the wafers are described in detail. The characterisation includes the determination of the band-gap energy, the lattice mismatch of the GalnAsP active layer to InP as a function of the melt composition, and the measurement of the optical-gain spectra. Oxide-stripe geometry lasers, prepared from the wafers, lase at around 1.3μm with pulsed thresholds between 300 and 400 mA. Some samples have been tested in c.w. operation at room temperature for more than 1400 hours. During the first 1000 hours a threshold increase of typically 2% has been observed.

DOI:10.1049/ij-ssed.1979.0037

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Various models for calculation of refractive indices in semiconductor laser materials are discussed and the results for GalnAsP compounds are compared. It is shown that the modified single-oscillator model appears to be the most reliable. The group index is also considered since it can be found easily from measurements of laser spectra. The value of the group index is more model sensitive than the refractive index, but it is also a function of the active-layer thickness in double heterostructures as a consequence of waveguide dispersion. A simple formula connecting group and phase indices for a symmetrical dielectric slab waveguide is derived and used to calculate the effective group index for double-heterostructure lasers

DOI:10.1049/ij-ssed.1979.0038

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The growth and properties of GaAs1- xSbx/Ga1-yAlyAs1-xSbxdouble-heterostructure (d.h.s.) lasers have been investigated. We have obtained lasers with an antimony content up to x = 0.17 emitting at wavelengths up to 1.12 μm at room temperature for pulsed currents as low as 120 mA. The d.h.s.s were grown by liquid-phase epitaxy on GaAs substrates. The lattice mismatch problem was overcome by growing up to ten ternary GaAs1-xSbxlayers of graded Sb composition. A study of quaternary GaAlAsSb layer growth has shown the effect of initial saturation of the melt on the Al content of the resulting solid. To overcome this problem a special epitaxial process has been developed to grow quaternary layers with controlled aluminium content. The relative amounts of Al and Sb were determined by a photoluminescence technique which also allowed us to evaluate the band-gap energy step between the active and confinement layers. A study of the temperature dependence of the threshold current was also made for d.h.s having different aluminium compositions. Threshold current density was found to vary as expT/To, whereToreaches 150 K for the highest aluminium content.

DOI:10.1049/ij-ssed.1979.0039

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Conventional models of junction heating in semiconductor lasers have been considered, and are found to be inconsistent with the experimental observations on stripe-geometry double-heterojunction lasers. In particular, the onset of the thermal runaway of c.w. threshold current, induced either by increasing the heat-sink temperature or by degradation processes, is found to occur at a current much less than predicted theoretically. Part of the reason for these inconsistencies is that at high temperatures there is a departure from the commonly assumed exponential dependence of pulsed threshold on junction temperature. However, it is the observation that the temperature rise of the active region is not directly proportional to the input power which explains why the experimental results are so different from the theoretical predictions. The results are discussed with reference to a model of multiple heat sources, with sources assuming different relative importance as the input power increases.

DOI:10.1049/ij-ssed.1979.0040

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Laser threshold currents increase with temperature, and appreciable heat has to be dissipated from the device while it is lasing. Low thermal impedance is therefore essential for c.w. operation at high temperatures and will also extend c.w. operating life at any temperature. Life tests at elevated temperatures on our lasers showed that, in the initial stages of ageing, increases in thermal impedance were dominant. Recent improvements in chip processing have increased the stability of the chip lasing parameters to the point where thermal impedance ageing is significant even at room temperature.1In this paper, we describe failure analyses of early lasers, discuss possible solutions to the thermal-impedance ageing problem, and finally report controlled life tests of several improved metallisations which eliminate the problem.

DOI:10.1049/ij-ssed.1979.0041

出版商:IEE    

年代:1979

数据来源: IET

摘要:

A detailed experimental investigation of a SiO2insulated GaAlAs laser is performed. The results are compared with theoretical calculations, including strain from the SiO2layer, and good agreement is found. The theory can account for a kink seen in the light/cunent characteristic.

DOI:10.1049/ij-ssed.1979.0042

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The 3-dimensional waveguide problem for stripe-geometry D.H. lasers is solved by an iterative method. The method allows one to self consistently determine the effective dielectric constant. Self-consistent solutions for stripe lasers with symmetric Epstein profiles in the junction plane are compared with approximate solutions obtained by ignoring the influence of the lateral waveguide on the solution of the transversewaveguide problem. It is shown that the approximate method, used previously, can lead to a considerable overestimation of the near-field half width of the fundamental lateral mode.

DOI:10.1049/ij-ssed.1979.0043

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Mode locking of semiconductor injection lasers is considered theoretically through the use of rate equations. The laser losses, rather than the material gain bandwidth, are found to limit the pulse width. Estimates for power output and the effects of spontaneous emission can be made

DOI:10.1049/ij-ssed.1979.0044

出版商:IEE    

年代:1979

数据来源: IET