Step structure and ordering in Te-doped GaInP

Abstract

The step structure and CuPt ordering in GaInP layers grown by organometallic vapor phase epitaxy on singular GaAs substrates have been investigated as a function of Te (DETe) doping using atomic force microscopy, and electrical and optical properties measurements. The degree of order decreases for Te concentrations of >1018 cm−3. It is estimated from the photoluminescence peak energy to be approximately 0.5 for undoped layers and the layers are completely disordered at sufficiently high Te doping levels. The bandgap energy is changed by 110 meV as the Te doping level increases from 1017 to 1018 cm−3. The step structure also changes markedly over the range of doping that produces disordering, from a mixture of monolayer and bilayer steps for undoped layers to solely monolayer steps for electron concentrations exceeding 1018 cm−3. For growth at 670 °C, the spacing between [1̄10] steps increased by over an order of magnitude as the doping level was changed over the range investigated, while the step spacing between [110] steps increased only slightly. In general, Te doping significantly improves the surface morphology viewed using atomic force microscopy. The degree of order and surface structure are changed at exactly the same doping concentration. This suggests that the disordering may be controlled by the fast propagation of [1̄10] steps due to kinetic effects at the step edges. A qualitative model is presented to explain these effects.