A new current-injection heterostructure laser: The double-barrier double-heterostructure laser

A new semiconductor current injection heterostructure laser, the double-barrier double-heterostructure (DBDH) laser, is fabricated by incorporating a pair of very thin (250–450 Å) unidirectionally graded barriers of very wide band gaps (≳ 2.00 eV) between the active layer and the uniform cladding layers of the conventional double-heterostructure laser. As a result, the beam divergence of this new heterostructure laser can be independently varied by changing the AlAs composition of the uniform cladding layers without affecting the temperature stability of the threshold Ith, the external differential quantum efficiency ηD, and possibly the reliability of the laser. With these lasers, excellent temperature stability of Ith , ηD spontaneous emission level, and abrupt transition from a light-emitting diode mode to laser mode were achieved and maintained up to temperatures as high as 276 °C. Narrow beam divergence ∼ 26° and low Ith ∼1 kA/cm2 were also obtained simultaneously from the same lasers. The present DBDH laser wafers were grown by molecular beam epitaxy.