David G. Seiler

Characterization of two‐dimensional dopant profiles: Status and review

The National Technology Roadmap for Semiconductors calls for development of two‐ and three‐dimensional dopant profiling methods for calibration of technology computer‐aided design process simulators. We have previously reviewed 2D dopant profiling methods. In this article, we briefly review methods used to characterize etched transistor cross sections by expanding our previous discussion of scanned probe microscopy methods. We also mention the need to participate in our ongoing comparison of analysis results for test structures that we have provided the community.

Semiconductor Characterization: Present Status and Future Needs

Contents: 1. Drivers for Silicon Process Development and Manufacturing. 2. Metrology Requirements for Beyond 0.35-um Geometries 3. Silicon Wafers, Gate Dielectrics, and Process Simulation. 4. Interconnects and Failure Analysis. 5. Critical Analytical Methods. 6. In-Situ, Real Time Diagnosis, Analysis, and Control. 7. Frontiers in Compound Semiconductors.

Multicarrier characterization method for extracting mobilities and carrier densities of semiconductors from variable magnetic field measurements

A simple, practical method is described to extract the carrier concentration and mobility of each component of a multicarrier semiconductor system (which may be either a homogeneous or multilayered structure) from variable magnetic field measurements. Advantages of the present method are mainly due to the inclusion of both the longitudinal and transverse components of the conductivity tensor and normalization of these quantities with respect to the zero‐field longitudinal component of the conductivity tensor. This method also provides a simple, direct criterion by which one can easily determine whether the material under test is associated with a one‐carrier or multicarrier conduction. The method is demonstrated for a simple one‐carrier system [GaAs single‐channel high‐electron‐mobility‐transistor (HEMT) structure] and two multicarrier systems (an InGaAs‐GaAs double‐channel HEMT structure and two types of carriers present in an InGaAs single‐channel HEMT structure). The analysis of the experimental data obtained on these samples demonstrates the utility of the method presented here for extracting carrier concentrations and mobilities in advanced semiconductor structures.

Temperature dependence of the energy gap of InSb using nonlinear optical techniques

We report the first use of the resonant two‐photon photo‐Hall effect as a nonlinear optical technique to measure the temperature dependence of the energy gap of InSb. Values of Eg for the temperature range 2–210 K are determined and compared with theoretical predictions and past experimental work. The technique is shown to provide an accurate, straightforward means of measuring Eg as a function of temperature in semiconductor materials.

Temperature and Composition Dependence of the Energy Gap of Hg1-xCdxTe by Two-Photon Magnetoabsorption Techniques

Accurate determinations of the energy gap Eg at liquid helium temperatures in alloys of 0.24≤x≤0.30 have been made by two‐photon magnetoabsorption techniques. They are shown to help verify the use of the Hansen–Schmit–Casselman (HSC) relation over the range 0<x<0.30 at these temperatures. In contrast, the observed temperature dependence of Eg below 77 K is nonlinear and thus cannot be described accurately by the HSC relation. Analysis of Eg (T) data for three samples with 0.24≤x≤0.26 has allowed the deduction of a new relationship for Eg (x,T) that more properly accounts for the nonlinear temperature dependence below 77 K and the linear behavior above 77 K, while still accurately describing the x dependence Eg(x,T) =−0.302 +1.93x +5.35(1−2x)(10−4) [(−1822+T 3)/(255.2+T 2)] −0.810x2 +0.832x3, for Eg in eV and T in K. This relation should apply to alloys with 0.2<x<0.3. The maximum change from the HSC relation in this range is 0.004 eV for x=0.2 at ∼10 K.

Characterization of molecular‐beam epitaxially grown HgTe films by Shubnikov–de Haas measurements

The oscillatory magnetoresistance (the Shubnikov–de Haas effect) has been used to investigate both three‐ and two‐dimensional electronic properties of films (∼2 μm thick) of HgTe grown by molecular‐beam epitaxial methods. Two‐dimensional behavior is found to arise from electrons constrained in an accumulation layer near the CdTe–HgTe interface on samples grown on (112) oriented CdTe substrates. Electron densities and effective masses of three electric subbands in two samples with different total densities are determined. The masses of lower subbands are higher, their values decreasing with decreasing total electron density and converging to the bulk value at low densities. This agrees with predictions of a triangular potential‐well model and a pronounced band nonparabolicity. Lower subbands are characterized by higher Dingle temperatures.

Intrinsic carrier concentration of narrow‐gap mercury cadmium telluride based on the nonlinear temperature dependence of the band gap

The intrinsic carrier concentrations of narrow‐gap Hg1−xCdxTe alloys have been calculated as a function of temperature between 0 and 300 K for x values between 0.17 and 0.30. The new and more accurate relation for the temperature dependence of the energy gap, which is based on two‐photon magnetoabsorption data, is used. This relation is further supported here by additional one‐photon magnetoabsorption measurements for x=0.20 and 0.23, which were made with a CO2 laser. In this range of composition and temperature, the energy gap of mercury cadmium telluride is small, and very accurate values for the gap are needed to obtain reliable values for the intrinsic carrier density. Kane’s k⋅p theory is used to account for the conduction‐band nonparabolicity. Large percentage differences occur between our new calculations and previously calculated values for ni at low temperatures. A nonlinear least‐squares fit was made to the results of our calculations for ease of use. The implications of these results for Hg1−xC...

Nonlinear oscillations and chaos in n-InSb

Abstract We present evidence for chaotic behavior in n-InSb. The Hall voltage exhibits a period-doubling route to chaos as the (non-ohmic) dc current is increased. The nonlinear oscillation and bifurcation processes are strongly influenced by irradiation with CO2 laser radiation.

Shubnikov-de Haas measurements on n- and p-type HgTe-CdTe superlattices

Oscillatory magnetoresistance (Shubnikov–de Haas) measurements have been used to determine free‐carrier effective masses in HgTe‐CdTe superlattices. Measurements on an n‐type superlattice yield an electron mass that is in excellent agreement with theoretical results from a tight‐binding band‐structure calculation. The p‐type data are more complex, showing evidence for a light‐hole mass at low magnetic fields and a much heavier mass at fields above 2.0 T. This finding is also in agreement with the predictions of band‐structure theory.

New method of characterizing majority and minority carriers in semiconductors

A novel characterization method using magnetoconductivity tensor components to determine the carrier concentration and mobility of majority and minority carriers is presented. Results are given for bulk n‐HgCdTe (one carrier), liquid phase epitaxial n‐HgCdTe (two carriers), and p‐InSb (two or three carriers). Advantages of this method over the standard Hall coefficient analysis are discussed.