The effect of ion implantation on structural damage of сompositionally graded AlGaN layers

Abstract

Compositionally graded Al x Ga 1-x N alloys with the Al concentration in the (7 ≤ x ≤ 32) range were implanted with Ar + ions to study the structural and strain changes (strain engineering). It was shown that ion implantation leads to ~0.3…0.46% hydrostatic strains and a relatively low damage of the crystal structure. The ion-implantation leads mainly to an increase of the density of point defects, while the dislocation configuration is almost unaffected. The density of microdefects is sufficiently reduced after the postimplantation annealing. The structural quality of the Al x Ga 1-x N layers strongly depends on the Al concentration and is worsen with increasing Al. The implantation induced structural changes in highly dislocated Al x Ga 1-x N layers are generally less pronounced. Based on the X-ray diffraction, a model is developed to explain the strain field behavior in the Al x Ga 1-x N/GaN heterostructures by migration of point defects and strain field redistribution. The approach to simulate 2θ/ω scans using statistical dynamical theory of X-ray diffraction for implanted compositionally graded structures AlGaN has been developed.

Simulating the effect of Ar+ energy implantation on the strain propagation in AlGaN

“…The analysis of the depth profiles provides interesting information about the strain induced in the ion implantation process. In contrast with what was found in the literature [27,55], it was possible to simulate the diffractograms with a small number of layers. In the aforementioned works up to 50 layers were used.…”

GaN-based power high-electron-mobility transistors on Si substrates: from materials to devices

“…Consequently, although a thick crack-free GaN film could be obtained by inserting the multi-layered LT-AlN buffer, it was not suitable for the preparation of HEMTs with strict GaN crystal quality requirements. (2) AlGaN buffer layers include step-like graded AlGaN [97] and linearly graded AlGaN structures [98,99], where the Al composition gradually changes from an AlN nucleation layer to GaN [100], the gradual change of the lattice constant and thermal expansion coefficient from AlN to GaN being achieved by the graded AlGaN buffer layer [101]. On the one hand, the AlGaN buffer layers between the AlN and the GaN introduce compressive stress during the growth process to compensate for the tensile stress generated during cool down from the growth temperature, improving the crystal quality and surface roughness of the GaN film [102,103].…”