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Disusun oleh: Agustian Noor
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| bet | 51/57 | | Sana | 09.05.2021 | | Hajmi | 0.62 Mb. | | #14427 |
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Fig. 6.6.3 Comparison of the theoretical low frequency capacitance (solid line) and the experimental data (open squares) obtained in the dark. Also shown is the high frequency measurement in the presence of light of the MOS capacitor (filled squares) and the low and high frequency capacitance obtained with the simple model (dotted lines). Fitting parameters are Na = 3.95 x 1015 cm-3 and tox = 80 nm.
Non-Ideal effects in MOS capacitors
Non-ideal effects in MOS capacitors include fixed charge, mobile charge and charge in surface states. All three types of charge can be identified by performing a capacitance-voltage measurement.
Fixed charge in the oxide simply shifts the measured curve. A positive fixed charge at the oxide-
semiconductor interface shifts the flatband voltage by an amount which equals the charge divided by the oxide capacitance. The shift reduces linearly as one reduces the position of the charge relative to the gate electrode and becomes zero if the charge is located at the metal-oxide interface. A fixed charge is caused by ions which are incorporated in the oxide during growth or deposition.
The flatband voltage shift due to mobile charge is described by the same equation as that due to fixed charge. However the measured curves differ since a positive gate voltage causes mobile charge to move away from the gate electrode, while a negative voltage attracts the charge towards the gate. This causes the curve to shift towards the applied voltage. One can recognize mobile charge by the hysteresis in the high frequency capacitance curve when sweeping the gate voltage back and forth. Sodium ions incorporated in the oxide of silicon MOS capacitors are known to yield mobile charge. It is because of the high sensitivity of MOS structures to a variety of impurities that the industry carefully controls the purity of the water and the chemicals used.
Charge due to electrons occupying surface states also yields a shift in flatband voltage. However as the applied voltage is varied, the fermi energy at the oxide-semiconductor interface changes also and affects the occupancy of the surface states. The interface states cause the transition in the capacitance measurement to be less abrupt. The combination of the low frequency and high frequency capacitance allows to calculate the surface state density. This method provides the surface state density over a limited (but highly relevant) range of energies within the bandgap. Measurements on n-type and p-type capacitors at different temperatures provide the surface state density throughout the bandgap.
Resistor
Pada dasarnya semua bahan memiliki sifat resistif namun beberapa bahan seperti tembaga, perak, emas dan bahan metal umumnya memiliki resistansi yang sangat kecil.
Bahan-bahan tersebut menghantar arus listrik dengan baik, sehingga dinamakan konduktor. Kebalikan dari bahan yang konduktif, bahan material seperti karet, gelas, karbon memiliki resistansi yang lebih besar menahan aliran elektron dan disebut sebagai insulator.
Bagaimana prinsip konduksi, dijelaskan pada artikel tentang semikonduktor.
Resistor adalah komponen dasar elektronika yang digunakan untuk membatasi jumlah arus yang mengalir dalam satu rangkaian. Sesuai dengan namanya resistor bersifat resistif dan umumnya terbuat dari bahan karbon .
Dari hukum Ohms diketahui, resistansi berbanding terbalik dengan jumlah arus yang mengalir melaluinya. Satuan resistansi dari suatu resistor disebut Ohm atau dilambangkan dengan simbol < (Omega).
Tipe resistor yang umum adalah berbentuk tabung dengan dua kaki tembaga di kiri dan kanan. Pada badannya terdapat lingkaran membentuk gelang kode warna untuk memudahkan pemakai mengenali besar resistansi tanpa mengukur besarnya dengan Ohmmeter.
Kode warna tersebut adalah standar manufaktur yang dikeluarkan oleh EIA (Electronic Industries Association) seperti yang ditunjukkan pada tabel berikut. Waktu penulis masuk pendaftaran kuliah elektro, ada satu test yang harus dipenuhi yaitu diharuskan tidak buta warna. Belakangan baru diketahui bahwa mahasiswa elektro wajib untuk bisa membaca warna gelang resistor (barangkali).
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