G.Sh. Gildenblat

A semi-empirical model of the MOSFET inversion layer mobility for low-temperature operation

This paper reports on a semi-empirical model of the mobility in the inversion layer of enhancement-type MOSFETs operated at low temperatures. The n-channel model is based on three different scattering mechanisms important at cryogenic temperatures--phonon, Coulomb, and surface roughness scattering. It is shown that the degradation of the mobility with the vertical field is accelerated at low temperatures and has a different functional form compared to that at the above room temperature. The p-channel model is the extension of a high-temperature model. The simple analytical expression presented here is suitable for use in a circuit simulation program like SPICE. The definition and the temperature dependence of the effective normal field are reexamined for both n- and p-channel devices.

Electrical characteristics of Schottky diodes fabricated using plasma assisted chemical vapor deposited diamond films

Schottky diodes were fabricated using gold and aluminum contacts to thin diamond films obtained by a microwave plasma assisted chemical vapor deposition process. The current‐voltage and capacitance‐voltage‐frequency characteristics of these devices are similar to those fabricated on a crystalline diamond base formed by traditional ultrahigh pressure process.

The barrier height of Schottky diodes with a chemical-vapor-deposited diamond base

A barrier height of 1.13±0.03 eV was measured for Al and Au rectifying contacts to p‐type chemical‐vapor‐deposited diamond thin films using the internal photoemission technique. The results are compared with experimental data reported for Schottky barriers on single‐crystal diamond.

Electrical properties of selectively grown homoepitaxial diamond films

Boron‐doped homoepitaxial diamond films were selectively grown using sputtered SiO2 as a masking material. Uniform thickness, down to 50 nm, over a large area can be achieved with this technique. Hall mobility of selectively grown films is comparable to that of high‐pressure high‐temperature synthetic bulk diamond with a corresponding carrier concentration.

Rectification and internal photoemission in metal/CVD diamond and metal/CVD diamond/silicon structures

Schottky diodes were formed with free-standing polycrystalline thin film diamond base as well as with polycrystalline diamond films grown on crystalline silicon. Current-voltage and internal photoemission measurements were used to characterize the Schottky diodes and the diamond film. Internal photoemission measurements yielded a barrier height of 1.15 eV. A comparison of experimental data for metal contacts to free-standing diamond films and those on silicon substrates indicates that both rectification and internal photoemission originate at the metal/diamond interface.

Oxygen based electron cyclotron resonance etching of semiconducting homoepitaxial diamond films

Oxygen‐based electron cyclotron resonance (ECR) plasma etching of boron doped homoepitaxial diamond films with no de bias has been achieved. The process was developed to the point where it can provide a uniform and reproducible etching procedure that yields smooth damage‐free etched surfaces. Etch rates attained under these conditions of smooth damage‐free etched surfaced were about 86 A/min.

Temperature dependence of electron trapping in metal‐oxide‐semiconductor devices as a function of the injection mode

Temperature dependence of electron trapping in metal‐oxide‐semiconductor (MOS) devices is controlled by the injection mode. In particular, for avalanche, photoinjection, or hot‐carrier injection the electron trapping and device degradation are accelerated at 77 K. However, for the tunneling injection the electron trapping decreases as the temperature is reduced. In this injection mode the temperature dependence of the electron trapping is similar to that of the SiO2 breakdown, which indicates that the two phenomena may be related. The temperature dependence of MOS breakdown is investigated experimentally in the 77–400‐K temperature range. It is shown that the corresponding activation energy changes drastically between 200 and 300 K.

Correction factor in the split C–V method for mobility measurements

Abstract We present experimental and theoretical results concerning the accuracy of the split C – V method. The correction factor is introduced and computed as a function of terminal voltages, temperature, doping concentration and oxide thickness. Theoretical computations are compared with experimental data for two groups of n -channel and p -channel MOS transistors fabricated using dual-type poly-gate CMOS process.

Space-charge-limited currents in materials with nonlinear velocity-field relationships

A general parametric form of the current-voltage characteristic of space-charge-limited currents (SCLC) is derived in the virtual cathode approximation. The result is used to obtain several new exact solutions for the trap-free insulator that is characterized by a nonlinear velocity-field (ν - F) relationship. Unlike previously reported results, the new solutions describe the gradual transition from the regime of constant mobility to that of the field-independent drift velocity. The first- and second-order corrections to the Mott-Gurney law then are obtained in a closed form for an important class of velocity-field relationships. Exact solutions are also Obtained for ν - F models that exhibit negative differential mobility behavior. The theory developed in this work is in good agreement with existing experimental data. The general result is used to specify the Condition that allows us to extract the anode field as well as the ν - F dependence from experimental current-voltage characteristics without assuming any a priori ν - F relation. In particular, such extraction is possible for the ideal trap-free insulator or materials with shallow traps. We illustrate the new approach by utilizing available experimental data to extract the ν - F dependence in GaAs.

Charge trapping and dielectric breakdown in MOS devices in 77-400 K temperature range

We report the results of an experimental investigation of the temperature dependence of electron trapping and dielectric breakdown in MOS devices operated in the 77–400 K temperature range. In contrast to avalanche or hot-electron injection investigated previously, the trapping of electrons in the regime of tunneling injection is suppressed at low temperatures. This result is related to the retardation of the time dependent dielectric breakdown observed for the low temperature operation of MOS devices. It is shown that both the failure rate and the temperature dependence of the time dependent dielectric breakdown is reduced for the low temperature operation. If Arrhenius law is used to describe the maximum number of carriers which can be injected into SiO2 prior to dielectric breakdown, then for temperature between 77 and 200 K the activation energy is reduced by approximately an order of magnitude as compared to its room temperature value.