Author: Julie Nkanta

Publisher:

Published: 2008

Total Pages: 0

ISBN-13:

This thesis studies the characterization and simulation of long wavelength indium aluminium gallium arsenide (InAlGaAs) lattice-matched to indium phosphide (InP) diode laser, emitting between 1.648 to 1.7 mum in wavelength. The active region of one laser diode sample consists of six In0.69Ga 0.31As quantum wells (1.0% compressive strain) and seven In0.52 Al0.36Ga0.12As unstrained barriers. The lasers are grown using digital alloy molecular beam epitaxy (MBE). The band diagram analysis shows a large conduction band offset which is typical of InAlGaAs lasers. The geometry-dependent and temperature-dependent measurement as well as the laser optical gain, loss and spectral properties were carried out and comparison done for different ridge widths (1.2 to 2.8mum), cavity lengths (555 to 2200mum) and temperature range between 25 and 70°C. The output power as a function of current characteristics reveals threshold current increase with cavity lengths and ridge widths with thermal roll-off occurring at higher injection currents. The slope efficiency and external differential quantum efficiency increases for the narrowest and widest ridge widths within the same cavity length laser device but decreases with increase in cavity length. The temperature analysis shows longer cavity length lasers exhibit better temperature characteristic than the shorter cavity length laser devices indicating the better thermal stability of the longer cavity lasers. Temperature elevations also caused increase in threshold current and decrease in efficiencies. The temperature distribution shows a higher temperature in the active region than the operating temperature due to self heating of the laser devices in continuous wave operation. The optical spectrum exhibits red-shifting of the emission wavelength with increasing bias current and temperature.