Step structure and ordering in Te-doped GaInP

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 >10(18) 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 10(17) to 10(18) cm(-3). The step structure also changes markedly over the range of eloping that produces disordering, from a mixture of monolayer and bilayer steps for undoped layers to solely monolayer steps for electron concentrations exceeding 10(18) cm(-3). For growth at 670 degrees C, the spacing between [(1) over bar 10] 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 [110] steps due to kinetic effects at the step edges. A qualitative model is presented to explain these effects. (C) 1998 American Institute of Physics. [S0021-8979(98)02017-9].