Nitride-based compound semiconductor and nitride-based compound semiconductor device

A nitride-based compound semiconductor device, comprising:

• a heterogeneous substrate with respect to a nitride-based compound semiconductor;
• a buffer layer formed on the substrate;
• and
• a channel layer including the nitride-based compound semiconductor formed on the buffer layer, wherein
• the nitride-based compound semiconductor includes
• gallium (Ga) interstitial atoms,
• nitrogen atoms, and
• impurity atoms of a metal, at least one of the impurity atoms forming a compound with at least one of the Ga interstitial atoms,
• a Ga vacancy density in the channel layer is no less than 1017 cm−3 and no greater than 1018 cm−3,
• the impurity atoms are doped across the entire nitride-based compound semiconductor of the channel layer, the at least one impurity atom having, in a nitride-based compound semiconductor crystal of the channel layer, a bonding energy with the corresponding Ga interstitial atom that is greater than an activation energy for diffusion of the Ga interstitial atom and a cohesive energy that is equal to or lower than a cohesive energy of the nitride-based compound semiconductor crystal without the impurity atom,
• the buffer layer does not contain impurity atoms of the metal,
• the metal is Fe, and
• a doping concentration of the impurity atoms is no less than 5×1016 cm−3 and no greater than 5×1018 cm−3.

A nitride-based compound semiconductor, comprising:

• a substrate;
• a buffer layer formed on the substrate;
• and
• a channel layer including gallium nitride (GaN) and formed on the buffer layer, wherein
• the channel layer is doped with impurity atoms of an element having
• a bonding energy higher than a self-diffusion energy of a Ga interstitial atom in the channel layer, and
• a cohesive energy that is equal to or lower than a cohesive energy of a GaN crystal of the channel layer without the element, wherein
• a Ga vacancy density in the channel layer is no less than 1017 cm−3 and no greater than 1018 cm−3,
• at least one of the impurity atoms forms a compound with at least one Ga interstitial atom in the GaN crystal of the channel layer,
• the buffer layer does not contain the element, and
• a doping concentration of the element is no less than 5×1016 cm−3 and no greater than 5×1018 cm−3.