| CPC H10D 30/4755 (2025.01) [H10D 30/015 (2025.01); H10D 62/221 (2025.01); H10D 62/8503 (2025.01)] | 8 Claims |

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1. An improved high electron mobility transistor (HEMT) structure, comprising in order:
a substrate;
a nitride nucleation layer;
a nitride buffer layer comprising a metal dopant;
a nitride channel layer having a metal doping concentration less than a metal doping concentration of the nitride buffer layer; and
a barrier layer, wherein a two-dimensional electron gas is formed in the nitride channel layer along an interface between the nitride channel layer and the barrier layer;
wherein a metal doping concentration X at an interface between the nitride buffer layer and the nitride channel layer is defined as a number of metal atoms per cubic centimeter, and a thickness Y of the nitride channel layer is in microns (μm) and satisfies Y≤(0.2171)ln(X)−8.34.
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