A. Ghaffari

Electrically Pumped Hybrid Evanescent Si/InGaAsP Lasers

Hybrid Si/III-V, Fabry-Perot evanescent lasers are demonstrated, utilizing InGaAsP as the III-V gain material for the first time to our knowledge. The lasing threshold current of 300-mum-long devices was as low as 24 mA, with a maximal single facet output power of 4.2 mW at 15 degrees C. Longer devices achieved a maximal single facet output power as high as 12.7 mW, a single facet slope efficiency of 8.4%, and a lasing threshold current density of 1 kA/cm2. Continuous wave laser operation was obtained up to 45 degrees C. The threshold current density, output power, and efficiency obtained improve upon those of previously reported devices having a similar geometry. Facet images indicate that the output light is largely confined to the Si waveguide.

Effect of substrate tilting on molecular beam epitaxial grown AlGaAs/GaAs lasers having very low threshold current densities

Single quantum well, graded refractive index separate confinement heterostucture (SQW GRINSCH) lasers with well thicknesses in the range of 65–480 A have been grown by molecular beam epitaxy (MBE) on (100) and off of (100) by 4° toward (111) A substrates. The threshold current density appears to be independent of the well thickness in the range of 65–165 A due to the compensating effects of volume of inversion and optical confinement. Under optimum growth conditions, the tilted substrates led to lower threshold current densities, the lowest value being 93 A/cm2 for a 520‐μm‐long cavity laser with a 125‐A‐thick well. To our knowledge, this is by far the best ever reported threshold current density obtained in a semiconductor injection laser. Deviations from optimum growth conditions drastically increased the threshold current density on (100) substrates whereas the degradation for those on the tilted substrates was much less pronounced.

Continuous-wave operation of extremely low-threshold GaAs/AlGaAs broad-area injection lasers on (100) Si substrates at room temperature.

Room-temperature continuous-wave operation of large-area (120 microm x 980 microm) GaAs/AlGaAs graded-refractive-index separate-confinement heterostructure lasers on (100) Si substrates has been obtained. Minimum threshold-current densities of 214 A/cm(2) (1900-microm cavity length), maximum slope efficiencies of about 0.8 W/A (600-microm cavity length), and optical power in excess of 270 mW/facet 900-microm cavity length) have been observed under pulsed conditions.

Low‐threshold (∼600 A/cm2 at room temperature) GaAs/AlGaAs lasers on Si (100)

Low‐threshold graded‐refractive‐index GaAs/AlGaAs laser structures were grown on Si (100) by molecular beam epitaxy and tested at room temperature under a probe station. Broad area devices having widths of 110–120 μm and cavity lengths of ∼500–1210 μm exhibited threshold current densities as low as 600 A/cm2 and total slope efficiencies of as high as 0.75 W/A. The thresholds fell in the range of 600–1000 A/cm2 in three different wafers, and it is assumed that the quality of the facets accounts for most of the spread in results.

High speed modulation and CW operation of AlGaAs/GaAs lasers on Si

Microwave modulation and CW operation of AlGaAs lasers grown by MBE on Si substrates have been obtained for the first time. Ridge waveguide lasers(10µm×380µm) were modulated with a microwave signal up to 2.5GHz which is notable considering the structure used. Near and far field measurements indicated a single transverse mode and a narrow beam angle (4.8°). Finally, polarization measurements appear to show the solely TE nature of the emission.

Measurement of Au/GaAs/AlxGa1−xAs hetero‐Schottky barrier height and GaAs/AlxGa1−xAs conduction‐band discontinuity

A new hetero‐Schottky structure for the study of Schottky barriers and heterojunctions is discussed. Photoelectric measurements have revealed a correlation between Au/GaAs and Au/AlxGa1−xAs Schottky barrier heights and GaAs/AlxGa1−xAs heterojunction band offsets. The conduction‐band discontinuity ΔEc in the GaAs/AlxGa1−xAs system is determined, and the ratio ΔEc:ΔEg is found to vary between 69±5% and 58±5% for x=0.15–0.48.