Visible and Near-Infrared Quantum Well Laser Diodes Grown by Solid Source Molecular Beam Epitaxy
Abstract
The growth of near infrared quantum well (QW) laser diodes in the AlGaAs material system and visible QW laser diodes in the AlGaInP material system by solid source molecular beam epitaxy (MBE) is investigated. Procedures for fabrication, measurement, and analysis are developed on the more easily grown GaAs QW lasers. Several studies are performed on the GaAs QW lasers. Doping of the laser core with a p-i-n profile improves laser performance. Low growth temperatures result in lasers with high threshold current densities due to the formation of traps caused by interface states and a deep level near the QW interface region. High growth temperatures also cause increases in threshold currents due to the effects of Ga desorption. Threshold current is not observed to depend strongly on the width of the laser waveguide core. Fabrication of lasers with tilted facets is facilitated by using misoriented substrates. The lasers exhibit higher threshold current densities due to decreased facet reflectivity. The benefits of compressively strained active layers are demonstrated in a GaInAs QW laser. Growth of visible AlGaInP lasers lattice matched to GaAs substrates is performed using a novel valved cracker cell for solid phosphorus. The cell avoids the expense and possible toxicity associated with the use of phosphine common in other growth techniques. It also alleviates the problems encountered when using solid phosphorus in a conventional effusion cell. High quality AlGaInP material is grown using the cell. The quality of the AlInP and GaInP ternaries is comparable to or better than that grown by other techniques based on photoluminescence and Raman spectroscopy measurements. The material is found to be highly disordered. Adequate doping levels for laser operation are obtained in the AlGaInP quaternary. Growth stops at the QW/barrier interfaces are proven to be detrimental to laser performance. Appropriate choices of barrier Al composition and QW Ga composition allow for the uninterrupted growth of laser cores with compressively strained wells. Such a laser structure produces laser diodes emitting at 676 nm. Possible future research plans with the visible lasers are discussed.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- January 1993
- Bibcode:
- 1993PhDT........47V
- Keywords:
-
- VISIBLE QUANTUM WELL;
- Physics: Optics; Physics: Condensed Matter; Engineering: Materials Science