Pulsed MOS Capacitor

The generation lifetime is measured with the pulsed MOS capacitor or the gate-controlled diode technique. It is important to understand that the lifetime measured by this technique can, and generally does, give very different values from the recombination lifetime measured by one of the techniques indicated above. 

A semiconductor junction device in the non-equilibrium state is either forward or reverse-biased. During forward-bias there are excess carriers in the device. The source of the excess carriers is either a forward-biased junction or light incident on, and absorbed by, the device. A semiconductor without a pn junction but with ohmic conctacts or one without any contacts can only be excited by light or some other form of radiation such as X-rays, electrcMi beams etc. 

The photoconductive decay (PCD) lifetime measuring technique was one of the first lifetime characterization methods to be used. [70] As the name implies it uses optical excitation of e-h pairs. The carrier decay is monitored as a function of time following the termination of the optical pulse. Traditionally the sample is provided with contacts and the current is measured as a function of time. More recently, non-contacting techniques have been developed that make the method attractive because it is fast and non-destructive. 

PCD relies on a measurement of the change of the sample s resistivity when the optical excitation is terminated. A schematic measurement circuit is shown in Fig.5. The output voltage change, AV, is given by [61,71] 

For the constat current mode, in which the load resistance is large compared to the sample resistance, we find [61,71] 

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In contrast to r measurements, in which the decay of excess carriers is monitored the generation lifetime is determined from the reverse-biased pn junction leakage current or from the pulsed MOS capacitor (22.) latter and the more popular of the two, an MOS-C is pulsed into deep depletion and the capacitance is monitored as a function of time. An appropriate analysis of the C-t response yields t. ... 

Electrical Characterization of Semiconductor Materials and Devices 23 4.2.2 Generation Lifetime Pulsed MOS Capacitor... 

The pulsed MOS capacitor (MOS-C) method is the most common technique to measure the generation lifetime. To determine it is necessary for scr generation to be dominant For silicon devices this is generally true when the pulsed MOS-C measurement is done at room temperature. For Xg determination the MOS-C is pulsed from accumulation into deep depletion. As a result of thermal ehp generation the device relaxes to its inversion state. [21] To extract the generation lifetime the capacitance, C, is measured as a function of time, as shown in Fig. 10(a). From such a C-t plot one generates a Zerbst Plot. [89] A Zerbst plot is a plot of vs. (Cp/C-1). It is related to the device... 

Cu, Au PCD pulsed MOS capacitor for active layer quality, defect etching Borisenko and Dorofeev (1983) Lamedica et al. (2002) Borisenko et al. (1984)... 

As the next step, check whether pulses appear at the gate of power MOS-FET Ql. If not, check the path, (capacitor C14, transformer T2, resistors R2, R9 and clipping zener diodes D4, D5). If everything is OK insert the jumper which connects transistor Ql and transformer Tl. 

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