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CCD的控制能力,即单位电极面积所能处理的最大电荷密度Q_(max),是CCD的一个重要参数。我们知道,控制能力差就可能限制窄带半导体IR CCD的元数和探测率。IRCCD控制能力较小的原因是半导体的隧道击穿,它限制了时钟电压的允许值。带间隧道电流密度J_x取决于半导体的电场强度E_x和禁带宽度E_o式中C为由带间跃迁矩阵单元所决定的常数。由于带间隧道效应与E_x密切相关,因而带间隧道效应具有击穿的特性。公式(1)是用处在均匀场中的半导体推导出来的。但是,如果eφ_(?)>>E_(?)(e为电子电荷,φ_s为表面电位),通常,这一点在CCD中是能够实现的,那么,就可以用公式(1)来计算空间电荷区中的隧道电流。在这个区域内电场是不均匀的。这样,将(1)式沿空间电荷区宽度积分,便可算出CCD中的总的隧道电流密度。
The control ability of CCD, namely the maximum charge density Q_ (max) that the unit electrode area can handle, is an important parameter of CCD. We know that poor controllability may limit the number of elements and the detection rate of narrowband semiconductor IR CCDs. The reason why the IRCCD is less capable of controlling is the tunneling of the semiconductor, which limits the allowable value of the clock voltage. The tunneling current density J_x depends on the electric field intensity E_x of the semiconductor and the forbidden band width E_o, where C is a constant determined by inter-band transition matrix elements. The inter-band tunnel effect has the characteristic of breakdown because of the close relationship between the band-tunnel effect and E_x. Equation (1) is derived from semiconductors in a uniform field. However, if eφ _ (>>) >> E _ (?) (E is the electron charge and φ_s is the surface potential), this can usually be done in a CCD. Then, the space charge Tunnel current in zone. The electric field is not uniform in this area. Thus, integrating the equation (1) along the width of the space charge region yields the total tunneling current density in the CCD.