Semiconductor substrate and semiconductor element

Abstract

A semiconductor substrate of the present invention has: a substrate; a buffer layer on the substrate, said buffer layer being formed of a carbon-containing nitride semiconductor; a high-resistance layer on the buffer layer, said high-resistance layer being formed of a carbon-containing nitride semiconductor; and a channel layer on the high-resistance layer, said channel layer being formed of a nitride semiconductor. The semiconductor substrate is characterized in that the high-resistance layer has: a first region having a carbon concentration lower than that of the buffer layer; and a second region, which is provided between the first region and the channel layer, and which has a carbon concentration higher than that of the first region. Consequently, a leak current is reduced by improving crystallinity, while maintaining the high resistance of the high-resistance layer, and crystallinity of the channel layer formed on the high-resistance layer is also increased, thereby providing the semiconductor substrate wherein deterioration of electron mobility and generation of current collapse in the channel layer are suppressed.

Description

technical field [0001] The present invention relates to a semiconductor substrate and a semiconductor element, and the semiconductor element is fabricated using the semiconductor substrate. Background technique [0002] Semiconductor substrates using nitride semiconductors have been used for power elements and the like that operate at high frequencies and high outputs. In particular, as a power element suitable for amplifying in high frequency bands such as microwaves, submillimeter waves, and millimeter waves, for example, high electron mobility transistors (HEMTs) and the like are known. [0003] As a semiconductor substrate using a nitride semiconductor, a semiconductor substrate is known in which a buffer layer, a GaN (gallium nitride) layer, and a barrier layer composed of AlGaN (aluminum gallium nitride) are formed on a Si (silicon) substrate in accordance with the Sequentially layered. [0004] The lower layer (high-resistance layer) of the GaN layer can improve the...

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Problems solved by technology

[0005] On the other hand, if the upper layer of the GaN layer functions as a channel layer and forms a level for trapping carriers, it may become the main cause of current collapse (a phenomenon in which the reproducibility of output current characteristics deteriorates), Therefore, the concentration of carbon and the like must be sufficiently reduced (see Patent Documents 1-3)

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