N-type AlGaAs Bragg reflectors (DBRs) are an important part of optoelectronic devic-type AlGaAs Bragg reflectors (DBRs) are an important part of optoelectronic devices such as light-emitting diodes and vertical cavity surface emitting lasers and reducing the series resistance is critical to the performance of the device. In this paper, four kinds of modulation-doped 20-cycle N-type Al0.5Ga0.5As/AlAs DBR were grown on N-type GaAs substrate by MOCVD. The white light reflection spectrum measurement results show that the peak wavelength of the epitaxial wafer meets the requirements of red light band. The upper and lower electrodes were prepared for each of the four structures, and the IV characteristics were tested after Cleavaged. The results show that the series resistance of the epitaxial wafer with the AlGaAs layer concentration of 1×1019 cm-3 and the AlAs layer doping concentration of 5×1018 cm-3 is the smallest. The resistance value was 1.36×10 -6 Ω cm 2. It shows that the modulation doping method can effectively reduce the series resistance of DBR.
Low reverse-bias series resistance tunnel junctions (TJs) are the key to improving the performances of high efficiency multi-junction semiconductor laser diodes (MJLDs). In this paper, InGaAs QW TJ and InGaAs DQW TJ with single InGaAs layer and double InGaAs layers inserted into GaAs TJs separately, are proposed. TJ chips were fabricated by metal organic chemical vapor deposition (MOCVD) technology and semiconductor process. The measurement results of the devices display that the operating voltage of the InGaAs QW TJ and the InGaAs DQW TJ is lower than that of the GaAs TJ under the same injection current, whether it is a small current or a large current, and the InGaAs DQW TJ operating voltage is lower than that of the InGaAs QW TJ. Both GaAs TJ and InGaAs DQW TJ were applied to 1060 nm dual active region semiconductor laser diode. The ridge lasers with a strip width of 100μm and a cavity length of 2 mm were fabricated. The working voltage is reduced from 3.81 V to 3.38 V at 1 A drive current. Further experimental results indicate that the reverse-bias series resistance of InGaAs QW TJ and InGaAs DQW TJ is lower than that of GaAs TJ, and the performances of InGaAs DQW TJ are the best. This is of great significance to reduce the heat loss of MJLDs and improve its performances.
Aiming at the urgent demand of small volume, high efficiency and high power laser source in the field of laser ranging, we proposed a multi-active-regions mini-bar (MAMB) structure of semiconductor laser diodes, in which multi-active regions (or sub-LDs) are cascaded by reverse-biased tunnel junctions (TJs) transversely, meanwhile, several sub-cells composed of sub-LDs form mini-bar laterally. The entire structure was epitaxially grown on GaAs substrate by MOCVD. In order to minimize the additional series resistance introduced by the tunnel junction, InGaAs double quantum wells (DQWs) TJ is adopted. To increase the COMD level, each sub-LD uses an AlGaAs asymmetric large optical cavity, in which the active region is a compressive strained InGaAs DQWs. After the standard chip post-process, the MAMB was fabricated with the ridge-shaped sub-cells, which has a strip width of 200μm and cavity length of 1mm. The MAMB was then soldered on C-mount and mounted on TO3 to test at room temperature with a frequency of 20 Hz and a pulse width of 20 μs. The output power of a MAMB with 3 active regions and 3 sub-cells reaches 47.76 W (28 A), corresponding to a slope efficiency of 2.02 W/A, and the peak wavelength is 1060.6 nm. The results show that the MAMB structure could effectively improve the output power and reduce its volume.