Step structure and ordering in Zn-doped GaInP

GaInP grown on (001) substrates by organometallic vapor phase epitaxy is ty pically highly ordered. The driving force is due to the [(1) over bar 10] o riented P dimers on the surface. There are apparently additional kinetic fa ctors related to surface steps that also play a key role in the ordering me chanism. However, the mechanism remains undetermined. This work presents th e effects of Zn on the step structure and ordering during epitaxial growth. The degree of order is estimated from the low temperature photoluminescenc e peak energy to be approximately 0.5 for undoped epitaxial layers and the layers are completely disordered at Zn doping concentrations [from dimethyz inc (DMZn) addition to the system] of > 1.7 x 10(18) cm(-3). This is verifi ed by transmission electron diffraction results. As a consequence, the band gap energy increases by 110 meV as the Zn doping level is increased from 3 x10(17) to 1.7 x 10(18) cm(-3). The [(1) over bar 10] and [110]-step spacin g as well as the root-mean-square roughness are found to be unchanged over the range of doping that produces disordering for both singular (001) and v icinal substrates. This indicates the disordering mechanism induced by Zn d oes not involve the step edge adatom attachment kinetics as previously repo rted for Te. The disordering is believed to be caused by the intermixing of Ga and In due to the increase in diffusion coefficient caused by the intro duction of Zn. Modulation of the DMZn flow rate during growth has been used to grow heterostructures and quantum wells. No well boundaries were observ ed by transmission electron microscopy for thin wells, although both ordere d and disordered regions are observed in 50 nm "wells." This is believed to result from Zn diffusion between the layers during growth. (C) 1999 Americ an Institute of Physics. [S0021-8979(99)02116-7].