Influence of intermediate-temperature buffer layer on flicker noise characteristics of MBE-grown GaN thin films and devices

摘要

Gallium nitride epitaxial layers were grown by rf-plasma MBE on different buffer layer structures. Type Ⅰ buffer layer consists of a conventional AlN high-temperature buffer layer (HTBL). Type Ⅱ buffer layer consists of a GaN intermediate-temperature buffer layer (ITBL) grown on top an AlN HTBL. Measurement of flicker noise in metal―semiconductor―metal (MSM) structures on type Ⅱ buffer layers exhibited close to two orders of magnitude reduction in the noise level compared to those fabricated on type Ⅰ buffer structures. This shows that GaN thin films grown with the use of ITBL have significantly lower number of interface traps at the metal―semiconductor interface, which is attributed to be the main cause of the observed improvements in the optical properties of the devices. We also performed systematic studies on hot-electron degradation of the devices through the application of a large voltage bias. The data demonstrate substantial improvement in the hot-electron hardness for devices fabricated on type Ⅱ buffer layer structures.