Abstract
One of the most important applications for semiconductor lasers is in the field of optical fiber communications. Separately, the 1.3 and 1.55 μm LDs are currently available light sources for long-span communication systems. Further, 1.3-μm-wavelength LDs have lower loss and negligible dispersion for standard silica fibers. GaInAsP/InP series is the most popular material for the long-wavelength lasers attributed to its very large flexibility in material growth and device structure, especially in the multi-step growth and photonic integrated circuits. However, this material has poor temperature characteristics attributed to smaller conduction-band offset. Therefore, it is very important to significantly improve the device performances for 1.3 μm GaInAsP LDs for fiber communication systems. In this dissertation we first describe the 1.3 μm GaInAsP/GaInAsP CS-MQW RWG LDs grown by MOCVD technique. Observed via the PL spectra, the optimum widths of well and barrier layers are 4 nm and 10 nm, respectively. These as-cleaved 3.5-μm-ridge LDs under the CW condition exhibit an infinite threshold current density of 920 kA/cm2, a characteristic temperature of 60 K (or up to 75℃), and a red-shift rate of 0.30 nm/℃ at a cavity length of 900 μm. We next demonstrate the 1.3 μm GaInAsP/GaInAsP CS-MQW RWG LDs with GaInP-QB layers in the undoped SCH regions. Through PL measurements, the optimum Ga composition of GaxIn1-xP-QB, GaInP-QB thickness, and pair number of the GaxIn1-xP-QB are 0.09, 5-nm-thick, and one pair, respectively. The optimum GaInP-QB structure in the p-side SCH region exhibits the narrowest PL FWHM of 43.1 meV, and the lowest threshold current of 23 mA and the characteristic temperature of 52 K for the as-cleaved 3.5-μm-ridge LDs at a cavity length of 600 μm. Similarly, the LDs exhibit a lower infinite threshold current density of 690 A/cm2, a comparable characteristic temperature of 57 K (or up to 85℃), and a red-shift rate of 0.28 nm/℃ at a cavity length of 900 μm. On the other hand, we also present a novel structure for the 1.3 μm AlGaInAs/AlGaInAs SC-MQW GRINSCH LDs with the GaInAsP and AlGaInAs GC layers. This new LD structure exhibits a lower threshold current of 9 mA, a higher characteristic temperature of 80 K, a little red-shift rate of 0.4 nm/℃, and a higher relaxation frequency of 8.14 GHz. Without the coupling loss and damping factor, the 3-dB bandwidth of 13.1 GHz can be achieved.