Effect of substrate-induced strain in the transport properties of AlGaN/GaN heterostructures

This paper studies the effect of substrate-induced strain in the transport properties of AlGaN/GaN heterostructures grown on Si substrates by metal-organic chemical vapor deposition. Partial thinning of the original Si substrate by chemical dry etching has been used to induce controllable amounts of biaxial strain in the sample. After each etching step, Raman and Hall effect—Van Der Pauw measurements were performed as a function of remaining Si substrate thickness to study the residual biaxial strain and transport properties of the two-dimensional electron gas (2DEG). A 25% increase in the 2DEG density was obtained after removal of ∼30% of the total Si thickness. In addition, a 20% higher electron mobility has been observed under biaxial strain increase. This new technology has been applied to standard AlGaN/GaN transistors grown on Si substrates to increase their maximum current density by ∼20%.