Epilayer Resistivity Research Articles

Study on 3.3 kV Super Junction Field Stop Insulated Gate Bipolar Transistor According to Design and Process Parameters.

In this paper, we analyzed the electrical characteristics of 3.3 kV super junction FS IGBT as next generation power device by structural design. The device parameters were extracted by design and process simulation. Especially, to obtain optimal breakdown voltage, we researched the breakdown characteristic. To begin with, we confirmed that the breakdown voltage was decreased as trench depth was increased. And we analyzed the breakdown voltage according to p-pillar dose. As a result of experiment, we confirmed that the breakdown voltage was increased as p-pillar dose was increased. To obtain over 3.3 kV, the dose of p-pillar was 5×1013 cm-2, the resistivity of epi layer was 140 Ω·cm. We will extract design and process parameters considering on state voltage drop.

Double-Epilayer Structure for Low Drain Voltage Rating n-Channel Power Trench MOSFET Devices

Double-epilayer structures were studied for n-channel low-voltage power trench MOSFET devices with drain-to-source voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> ) of 20 V, and various device performance improvements have been observed. The threshold voltage variation (sigma <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Vth</sub> ) can be reduced by increasing the intrinsic epilayer thickness. A 9% effective electron mobility mu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> improvement has been observed and is attributed to the reduced background phosphorus scattering. A Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gd</sub> of 3.1 nC for double- epilayer structure is observed which is about 30% lower than the 4.5 nC for the single-epilayer structure. This improved Qgd is due to both an increasing depletion width at the bottom of the trench and the well junction moving toward the trench bottom for the double-epilayer structure. The dependence of Qgd on the double-epilayer structure (intrinsic epilayer thickness and the doped epilayer resistivity) is found following the power law Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gd</sub> prop alphaX <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-b</sup> , where a and b are double-epilayer structure dependent. Compared to the single-epilayer structure, a double- epilayer structure can handle larger reverse current, suggesting a smaller basis resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bb'</sub> ) for the double-epilayer structure. This improvement ranges from 7% to 24% depending on the die pitch. A 20% less temperature dependence of device on-resistance for the double-epilayer structure has also been observed. This enables a large forward current capability, although the mechanism is not well understood.

Homoepitaxial Growth of Iron-Doped 4H-SiC Using BTMSM and t-Butylferrocene Precursors for Semi-Insulating Property

In this paper, we attempted to grow semi-insulating SiC epitaxial layer by in-situ iron doping. Homoepitaxial growth of iron-doped 4H-SiC layer was performed by MOCVD using organo-silicon precursor, bis-trimethylsilylmethane (BTMSM, [C7H20Si2]) and metal organic precursor, t-butylferrocene ([C14H17Fe]). Doping-induced crystallinity degradation showed different tendency depending on conducting type of substrate. The crystal quality of epilayer grown on n-type substrate was not degraded significantly despite of the Fe doping but in case of semi-insulating substrate, crystallinity was remarkably degraded as increasing iron contents. For measurement of resistivity of highly resistive iron-doped 4H-SiC epilayer, we used the on-resistance technique which is firstly attempted for measuring resistivity of epilayer. From on-resistance of epilayer measured by I-V, it is shown that the residual donor concentration of epilayer was decreased as increasing partial pressure of t-butylferrocene. The resistivity of iron-doped 4H-SiC epilayer was about 107 Ωcm. From this result, it is concluded that Fe could effectively act as a compensation center in the iron-doped 4H-SiC.

Resistivity control of unintentionally doped GaN films

GaN epilayers were grown on sapphire substrates via low temperature GaN and AlN nucleation layers (NL) by metalorganic chemical vapor phase epitaxy (MOCVD). The morphology of the individual NLs strongly depends on the carrier gas used during the growth and recrystallization and this is the key factor for control of the resistivity of the GaN layer grown on it. The GaN nucleation layer grown in presence of N2 has a higher density of islands with a statistically smaller diameter than the samples grown in H2 atmosphere. The NL grown in N2 enables the growth GaN with a sheet resistivity higher than 3×104 Ω cm as opposed to a 0.5 Ω cm value obtained for the NL grown in H2. Introduction of an additional intermediate (IL) low temperature (GaN or AlN) nucleation layer changes the GaN epilayer resistivity to about 50 Ω cm, regardless of the carrier gas used during the growth of the IL. Defect selective etching demonstrated that control of the type and density of the dislocations in GaN enables the growth of highly resistive layers without any intentional acceptor doping (Mg, Zn). It will be demonstrated that by changing the ratio of edge type to screw dislocations the resistivity of the layer can be changed by a few orders of magnitude. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Dc and ac transport in molecular-beam-epitaxy-grown metal/ZnSe/GaAs heterojunction structures

The room-temperature electrical transport properties of ZnSe epilayers grown above the critical layer thickness on n+-GaAs substrates by molecular-beam epitaxy have been studied. dc current versus voltage and small-signal ac admittance versus voltage and frequency measurements were made on Schottky contacts (Au or Hg). A novel method of analysis is presented which, extending a previous model to include the three-dimensional effects of current spreading as a function of frequency, allows the ZnSe epilayer resistivity to be obtained. Combining this with the doping concentration obtained from analysis of the C-V characteristics, the ZnSe mobility may be calculated. Mobilities thus measured compare well with our own and other workers’ published Hall mobility data on similar samples, as well as with theoretical calculations. We believe that our results represent a unique and detailed characterization of an epilayer heterostructure on a highly conducting substrate.

Effect of growth parameters on the properties of GaN : Zn epilayers

The vapor-phase HCl/Ga/NH 3 method for deposition of GaN : Zn epilayers on sapphire substrates has been investigated to determine the dependence of epilayer resistivity, cathodoluminescence, and surface quality on the growth parameters. Both nucleation and control of the epilayer properties have been significantly improved by introducing HCl directly into the deposition zone in addition to the HCl that passes over the Ga source to produce GaCl. The effect of annealing on the stability of undoped layers and on the cathololuminescence of Zn-doped layers has also been investigated. Electroluminescent devices with reproducible properties have been obtained by growing structures consisting of an undoped n + layer, a Zn-doped n-type layer, and a very thin, Zn-doped, high-resistivity layer whose growth parameters determine the emission wavelength and electroluminescence efficiency.