Thin P-clad Research Articles

Low loss, thin p-clad 980-nm InGaAs semiconductor laser diodes with an asymmetric structure design

Thin p-clad InGaAs ridge waveguide quantum-well lasers having an asymmetric structure design were fabricated. The internal absorption coefficient is as low as 2.5 cm/sup -1/, due to the restricted field extension in the 0.3-μm-thick p-type top AlGaAs cladding layer. Ti-Pt-Au metallization is used outside the ridge to provide adherence on the oxide while Au directly contacts the ridge region. It is shown that the most likely source of loss in these thin p-clad devices is scattering at the rough interface between Au and the p/sup ++/ top GaAs layer, after ohmic contact heat treatment.

Antiguided array diode lasers fabricated with modulated cap thin p-clad structure

Antiguided array lasers were fabricated in thin p-clad, InGaAs-GaAs single quantum-well material. The required lateral refractive index variation was achieved by precisely modulating the thickness of the GaAs cap layer using a novel pulsed anodization/etching technique. Edge-emitting arrays having 20 lasers on 7-μm centers with 5-μm-wide gain regions were characterized. At 1.2 times the pulsed current threshold (I/sub th/), the central lobe of the lateral far field of the arrays contained about 75% of the beam power and was about twice the diffraction limit (FWHM=0.8/spl deg/). At 10×I/sub th/, the central lobe contained about 60% of the beam power and was about 1.6/spl deg/ wide.

ABNORMAL LASING BEHAVIORS IN THIN p-CLAD InGaAs QUANTUM WELL LASERS

Thin p-clad (250 nm) InGaAs quantum well (QW) lasers with 200 nm p +-GaAs cap layer thickness and various device configurations are studied. For wide stripe ( w=50 μm) lasers, abnormal lasing characteristics of very high thresholds, current on-time dependent lasing and micro-second long delays are observed. With 300 nm ridge-height, micro-second long lasing delays are found in w=6 μm lasers, and Q-switching in w=2.5 μm and 3.5 μm lasers, respectively. The unusual lasing behaviors are attributed to the decrease of transverse optical confinement caused by the increase of p +-GaAs cap layer thickness. To improve device performance and eliminate lasing delay, p +-GaAs cap layer thickness of wide stripe lasers and stripe width of narrow stripe devices have to be not greater than 170 nm and 1.5 μm, respectively, in thin p-clad (250 nm) laser structure.

Characterization of thin p-clad InGaAs single-quantum-well lasers

Low-ridge, thin p-clad InGaAs single-quantum-well (SQW) lasers with shiny Au contacts have been fabricated using a pulsed anodic oxidation technique. Although the ridge is very low (130 nm), the lateral refractive index step is sufficiently large to provide strong lateral waveguiding. Pulsed current measurements of threshold current, operating wavelength, and lateral far field as a function of ridge width are presented and compared with measured values reported for low-ridge and oxide-defined lasers fabricated from conventional thick p-clad material. The CW performance characteristics of five-micron-wide, low-ridge, thin p-clad lasers are shown to be comparable to those of conventional InGaAs SQW high-ridge waveguide lasers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Contact reflectivity effects on thin p-clad InGaAs single quantum-well lasers

Thin p-clad InGaAs quantum-well (QW) lasers with either Au or Ni as the p-contact metal have been fabricated. Due to reduced contact reflectivity, the Ni contact lasers hare significantly higher threshold currents and lower slope efficiencies than the Au contact lasers. In addition, operating wavelength differences greater than 50 mn are observed for cavity lengths between 250 and 700 microns, with large wavelength jumps occurring at shorter and longer cavity lengths. The measured wavelength effects are explained by incorporating the optical mode loss difference between the two laser types into quantum-well laser theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>