Metamorphic buffer layers for mid-infrared emitting semiconductor lasers

We have investigated the use of Metamorphic Buffer Layer (MBL) structures for the realization mid-infrared semiconductor lasers employing either interband or intersubband transitions. The resulting surface morphology of the MBL is generally cross-hatched along the orthogonal <;110> directions. This surface morphology may negatively impact device structures grown on top of the MBL. We have employed two different techniques to improve the surface morphology of MBLs, while maintaining an epiappropriate surface chemical composition and structure: (1) Introduction of Sb as a surfactant to create novel step-graded MBLs; and (2) Chemical-Mechanical-Polishing (CMP) of the MBL followed by MOCVD regrowth of layers atop the MBL.