Growth of InxGa1-xAs (0.0 </= x </= 0.3) Metamorphic Pseudosubstrates on (001) GaAs Wafers and the evolution of InAs Quantum Dots on These Substrates

Abstract

<p> InxGa1_xAs (0.00</= x </= 0.42) metamorphic pseudosubstrate layers (MSLs) were studied as a means to change the lattice constant of the substrates and to modify the growth conditions of InAs quantum dots (QDs) by varying the strain. The MSLs showed symmetrical mosaicity about the 110 axes but the spread was different in the two orthogonal [110] and [110] directions. The anisotropy in the mosaic spread in two < 11 O > directions was correlated to asymmetry of kinks and multilevel-terrace growth front during the growth of InxGa1_xAs buffer layers. X-ray and electron diffraction along with the least squares criterion can interchangeably be employed to determine the lattice constant of the MS Ls. It is possible to grow a defect free MSL with employing a compositional undershoot relative to the terminating buffer layer. Asymmetric tilt was found in an In0.42Ga0.58As MSL grown on a singular (001) GaAs substrate with an initial layer of a low temperature ( < 300 °C) grown InGaP prior to the growth of step-graded InxGa1-xAs (x = 0.02 to 0.42) buffer layers. The tilt around [110] axis was correlated with the imbalance of the tilt component of the Burgers vector (BV) of the 60° α-dislocations. Climb and jog formation of β-dislocations in the presence of P-interstitials were considered as a plausible mechanism for multiplication of the like-sign BV α-dislocations. These results show that an asymmetric tilt boundary can be induced in mismatched heterointerfaces grown on singular substrates. The evolution of InAs QDs on InxGa1-xAs(0.0</= x </= 0.3) MSLs on GaAs substrates was studied. The results indicate that the ratio of the height (h) over lateral diameter (d) of the QDs decreases with decreasing strain (i.e. the morphology of the coherent islands evolve toward a uniform film morphology (h/d=0) with deceasing strain). This evolution is analogous to the current </p>