Planarization and processing of metamorphic buffer layers grown by hydride vapor-phase epitaxy

Brian T. Zutter, Kevin L. Schulte, Tae Wan Kim, Luke J. Mawst, T. F. Kuech, Brendan Foran, Yongkun Sin

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Hydride vapor-phase epitaxy (HVPE) is a high-growth-rate, cost-effective means to grow epitaxial semiconductor material. Thick HVPE-based metamorphic buffer layers (MBLs) can serve as "pseudosubstrates" with controllable lattice parameter. In our structures, the indium content in In x Ga1-x As is gradually increased from zero to the final composition corresponding to the desired lattice constant, and then a thick (∼10 μm) constant-composition capping layer is grown. This thick capping layer promotes maximum strain relaxation while permitting use of polishing procedures to achieve surface planarity. Lattice-mismatched growth of MBLs invariably results in rough, cross-hatched surface morphology exhibiting up to 200 nm peak-to-valley roughness. This roughness can be eliminated by chemical mechanical planarization, thus creating a suitable surface for subsequent regrowth. Polishing of In x Ga1-x As is complicated by the sensitivity of the surface layer to the polishing parameters, particularly the applied pressure. Polishing at high applied pressure (12 psi) results in the formation of circular asperities hundreds of nanometers high and tens of microns in diameter. When lower applied pressure (4 psi) was used, the cross-hatching height of MBLs was lowered from 200 nm to <10 nm over a 350 μm lateral scale. The successfully planarized In0.20Ga0.80As MBLs were used as a substrate for a superlattice (SL) structure such as that used in quantum cascade lasers. Use of planarization before regrowth of the SL resulted in a reduction of the high-resolution x-ray diffraction peak full-width at half-maximum from 389′ to 159′.

Original languageEnglish
Pages (from-to)873-878
Number of pages6
JournalJournal of Electronic Materials
Issue number4
StatePublished - Apr 2014


  • Chemical mechanical planarization
  • InGaAs
  • hydride vapor-phase epitaxy
  • metamorphic buffer layers


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