Substrate system consisting of a metamorphic transition region comprising a laminate of AlxGa1-x N and the same material as the substrate.

摘要

A laminated substrate system containing a metamorphic transition buffer layer 2 made from a plurality of alternating layers of AlxGa1-xN (5) and a material of the same chemical composition as the supporting substrate material 1. The material AlxGa1-xN has a value of x according to 0 ¤ x ¤ 1. A III-Nitrides semiconductor device 3 with a low dislocation density is formed on top of the laminated substrate system. The multiple layers (4,5, fig 2) of the metamorphic transition region form a superlattice structure whose composition and lattice constant and thickness changes along its growth direction from that of the supporting substrate 1, in the vicinity of the supporting substrate, to that of the device 3 , in the vicinity of the device. The substrate preferably comprises of sapphire, silicon (Si) , silicon carbide (SiC) or gallium arsenide (GaAs). In the case of the sapphire substrate the metamorphic transition region comprises alternating layers of Al2O3 and AlxGa1-xN. The thickness of the layers constituting the metamorphic transition region is kept below the threshold where threading dislocations become present, thus limiting the growth of 3D crystals. In one embodiment having a sapphire substrate, the initial thickness of the Al2O3 layer is 5nm and that of the GaN layer is 0.3nm. Conversely the 92nd layer comprises a 0.3nm Al2O3 layer and a 5nm GaN layer. Deposition of the materials can be made by MOVPE, MBE, ALD. The invention finds applications in light emitting diodes (LEDs) , laser diodes, solar cells , heterostructure field effect transistors (HFETs) and high electron mobility transistors (HEMT).