Heterostructure laser
AssigneeUniversity of Southern California
InventorsThomas C. Hasenberg, Elsa M. Garmire
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Abstract
A semiconductor laser of the heterostructure type is grown on a p-type substrate and has a plurality of p-type active layers. In a preferred embodiment, the active layers are grown by liquid phase epitaxy from a single melt which is maintained just below its equilibrium temperature and is cooled very slowly during deposition. As a result, the active layers are substantially identical in composition and have a very low lattice mismatch. They emit light at characteristic wavelengths within 50 angstroms of each other, indicating that their modal gain envelopes coincide. This condition minimizes the threshold current.
Claims15
In a semiconductor laser of the heterostructure type, the improvement comprising:
- a p-type substrate having lower electrode means for establishing electrical connection thereto;
- a p-type lower confining layer overlying the substrate;
- a composite active region formed on the lower confining layer,
- the composite region having at least two p-type active layers separated by one or more p-type separation layers,
- the active layers being of substantially identical composition, and
- the active layers and the confining layers each being at least 300 angstroms thick;
- an n-type upper confining layer formed on the composite active region to produce a p-n junction therewith;
- upper electrode means for establishing electrical connection to the upper confining layer;
- the active layers having band gaps smaller than the band gaps of the confining layers and the separation layers;
- and
- means for applying an electrical potential between the upper electrode means and the lower electrode means to inject charge carriers into the active layers.
In a semiconductor laser of the heterostructure type, the improvement comprising:
- a substrate having lower electrode means for establishing electrical connection thereto;
- a lower confining layer overlying the substrate;
- a composite active region formed on the lower confining layer,
- the composite region having at least two active layers separated by one or more separation layers,
- the active layers being of substantially identical composition, and
- the active layers and the confining layers each being at least 300 angstroms thick;
- an upper confining layer formed on the composite active region;
- upper electrode means for establishing electrical connection to the upper confining layer;
- the active layers having band gaps smaller than the band gaps of the confining layers and the separation layers;
- and
- means for applying an electrical potential between the upper electrode means and the lower electrode means to inject charge carriers into the active layers;
- the substrate and the lower confining layer being of a first conductivity type,
- the upper confining regions being of a second conductivity type which is opposite to the first conductivity type, and
- the composite active region as a whole being of either the first or second conductivity type.
Dependencies are inferred from the claim text.