二极管PN结反向偏置时为什么不能流通电流,要求从半导体物理基础的角度回答,不能用已知结果证明提问。

2024-12-04 23:31:26
推荐回答(2个)
回答1:

第一个问题:
pn结外加正向偏置电压后,外电场削弱了pn结内电场(空间电荷区)的电压,即削弱了少子的漂移运动,继而使得空间电荷区变窄,使得多数载流子(P区多子是空穴;N区多子自由电子)形成扩散运动,且外电压越大,扩散运动越强,即表示电流越大;内电场与外电场的电压方向是相反的,所以,反之如果外加电压是反向偏置电压,那么会使得内电场电压增大,这样扩散运动被大幅减弱,反而使得少子漂移运动加剧,继而使得空间电荷区变宽,阻碍能力越强;正向偏置电流减小为0,这就是二极管PN结反向偏置时为什么不能流通电流的原因

第二个问题:
VCB>VBE 这是三极管饱和状态,之所以不能像二极管那样工作,是由于制造工艺造成的
在三极管制造时要求,发射极掺杂浓度高,基极薄且参杂浓度低,集电极面积比较大便于收集电子,但参杂浓度也低。 但二极管两个区得参杂浓度是一样,正是这一特点使得单向导电性能体现明显,应用也较广,所以如果有了这个浓度差,在反偏时没有多余的载流子出现,即表示有正向电流流过,那么二极管就变成一个可变电阻,它就不是二极管了,换句话说如果有了这个浓度差,单向导电的性能就被大幅度削弱,制造一个这样器件还不如来根导线替代更好,所以没有意义

回答2:

大学模电最好问老师,一次性搞清楚~

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