Since the 1980s, the standard story for why GaAs grown on silicon fills with antiphase boundaries: single-atom steps on the Si surface flip which sublattice Ga and As land on. Hence miscut wafers, tilted to pair those steps up.
A review posted this week argues the steps don't do it.
What it pulls together:
- DFT puts a charge-compensated GaP/Si interface at 23.4 to 27.3 meV/Ų, below abrupt interfaces (30 to 70). Half the top Si plane swaps for group-III atoms, one stable configuration everywhere.
- Growth starts as nm-scale 3D islands, each a single domain, spreading across many terraces. Too small for AFM, and their fast merging looks like a continuous film in TEM, which is how they were long read as 2D growth.
- At a step edge, changing the interface configuration costs far less energy than forming a boundary.
So the boundaries form where independently nucleated islands meet. In their thought experiment, one island would stay a single domain across any number of steps.
Miscut isn't free: it misaligns the crystal's natural cleavage planes, which complicates laser cavities. If the review is right, the thing to control is how islands nucleate and merge, not step structure.
Cornet et al., arXiv, 21 Sep