Temperature engineered growth of low-threshold quantum well lasers by metalorganic chemical vapor deposition

A new technique is demonstrated for the formation of narrow active regions in quantum well lasers. In temperature engineered growth (TEG), the substrate temperature is varied during the growth of epitaxial layers by metalorganic chemical vapor deposition (MOCVD) on nonplanar substrates, allowing two-dimensional control of device features. Buried heterostructure designs with submicron active region stripe widths are obtained without the need for fine process control of lateral dimensions. The contact area above the active region is coplanar with the surrounding surface and wide enough to allow easy contacting and heat sinking. Carrier confinement is accomplished by lateral thickness variation of the quantum well active region resulting in a local strip of minimum band gap. Lasers grown in this manner exhibit cw threshold currents as low as 3.8 mA (3.4 mA pulsed), having an as-grown active region width of 0.5 μm. The near-field optical profile indicates stable, single transverse mode operation and minimal current leakage in these devices.