Donor (English spelling)

Japanese: ドナー(英語表記)donor
Donor (English spelling)
An impurity element that has a higher valence than the parent element that constitutes the semiconductor. For example, when a group 15 element such as phosphorus, arsenic, or antimony is added as an impurity to a group 14 semiconductor such as silicon or germanium, four of the five outermost electrons of the impurity element are covalently bonded to the parent element. The remaining electron is not involved in the bond and is bound to the impurity element by a relatively weak force at low temperatures. When the temperature rises, this electron is released from the bound state and becomes a free electron in the conduction band. An impurity that donates a free electron to the conduction band in this way is called a donor. A donor impurity forms a donor level in the forbidden band and supplies electrons to the conduction band, so the semiconductor exhibits n-type conductivity. In the case of compound semiconductors, basically, an atom with a higher valence than the constituent atoms is a donor impurity, but the same impurity can act as a donor or an acceptor depending on the conditions of addition. Stoichiometric defects can also act as donors. (→ Impurity semiconductor )

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:
半導体を構成する母体元素の原子価よりも大きい原子価をもつ不純物元素をいう。たとえば,ケイ素 (シリコン) やゲルマニウムなどの 14族半導体に 15族元素であるリン,ヒ素,アンチモンなどを不純物として添加すると,これらの不純物元素の5個の最外殻電子のうち4個は母体元素との共有結合にあずかる。残りの1個の電子は,結合に関与せず,低温では不純物元素に比較的弱い力で束縛されている。温度が上昇すると,この電子は束縛状態から解放され,伝導帯で自由電子となる。このように伝導帯に自由電子を供給 (donate) するような不純物をドナー (または供与体) と呼ぶ。ドナー不純物は禁制帯の中にドナー準位を形成し,伝導帯に電子を供給するので,その半導体はn型伝導を示す。化合物半導体の場合,基本的には構成原子より原子価の大きい原子はドナー不純物となるが,同じ不純物でも添加する条件によりドナーとして作用したり,アクセプタとして作用したりする場合がある。また化学量論的欠陥もドナーとしての働きをする場合がある。 (→不純物半導体 )

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