Semiconductor device, nitride semiconductor wafer, and method for forming nitride semiconductor layer

摘要

According to one embodiment, a semiconductor device includes a functional layer of a nitride semiconductor. The functional layer is provided on a nitride semiconductor layer including a first stacked multilayer structure provided on a substrate. The first stacked multilayer structure includes a first lower layer, a first intermediate layer, and a first upper layer. The first lower layer contains Si with a first concentration and has a first thickness. The first intermediate layer is provided on the first lower layer to be in contact with the first lower layer, contains Si with a second concentration lower than the first concentration, and has a second thickness thicker than the first thickness. The first upper layer is provided on the first intermediate layer to be in contact with the first intermediate layer, contains Si with a third concentration lower than the second concentration, and has a third thickness.

主权项

1. A method for forming a nitride semiconductor layer, the method comprising forming a nitride semiconductor layer including a first stacked multilayer structure on a major surface of a substrate,
the first stacked multilayer structure including: a first lower layer of a nitride semiconductor; a first intermediate layer of a nitride semiconductor; and a first upper layer of a nitride semiconductor, the first lower layer containing Si with a first concentration and having a first thickness, the first intermediate layer being provided on the first lower layer to be in contact with the first lower layer, containing Si with a second concentration lower than the first concentration, and having a second thickness thicker than the first thickness, the first upper layer being provided on the first intermediate layer to be in contact with the first intermediate layer, containing Si with a third concentration lower than the second concentration, and having a third thickness, the forming the nitride semiconductor layer including: forming the first lower layer with a first V/III ratio and at a first temperature; forming at least a part of the first intermediate layer on the first lower layer to be in contact with the first lower layer with a second V/III ratio lower than the first V/III ratio and at a second temperature not less than the first temperature; and forming the first upper layer on the first intermediate layer to be in contact with the first intermediate layer with a third V/III ratio lower than the first V/III ratio and higher than the second V/III ratio and at a third temperature higher than the second temperature.