| Popis: |
Two different approaches are pursued to realize densely packed gallium (arsenic) antimonide (Ga(As)Sb) quantum dots (QDs) for efficient QD lasers. In the first method nano¬structures are realized by self-organization using mask-less dry-etching. GaSb cone structures are achieved with a maximum density of 1.2 ∙ 1011 cm-2. During etching a 5 nm thick amor¬phous Ga layer is formed, also the surface oxidizes immediately under atmosphere, and as a consequence the dots are optoelectronically inactive, thus no photoluminescence (PL) can be achieved. Several attempts are made to revoke these effects, but the nanostructures stay inactive. In the second approach self-assembled optoelectronically active GaAsSb QDs are grown on GaAs in Stranski-Krastanov mode. With these QDs efficient lasers are grown, exemplarily with an emission wavelength around 900 nm. In pulsed mode a minimum thres¬hold current density of jth = 121.7 A/cm2 and a maximum in differential quantum effi¬ciency of ηd = 0.66 are measured at T = 130 K. The internal quantum efficiency is ηi = 0.76 with internal losses of αi = 4.86 cm-1. |
