Mototsugu Ogura

ZnSe‐ZnS strained‐layer superlattice grown by low pressure metalorganic vapor phase epitaxy using methylalkyls

Good quality ZnSe‐ZnS strained‐layer superlattice (SLS) has been successfully fabricated for the first time by low pressure metalorganic vapor phase epitaxy (MOVPE) using methylalkyls (dimethylzinc, dimethylselenide, and dimethylsulfide). The satellite peak observed by x‐ray diffraction measurements and the periodic behavior of the atomic profiles by secondary ion mass spectrometry measurements confirm the formation of the SLS structure. From the photoluminescence measurements, the quantum size effect has been evidenced by the relationship between the ZnSe well‐layer thickness and the peak energy shift of the light emission. Our results show that low pressure MOVPE using VI group alkyls can be quite useful for the growth of ZnSe‐ZnS SLS.

A Capacitance Investigation of InGaAs/InP Isotype Heterojunction

We have measured deep levels near the InGaAs/InP heterointerface by DLTS and C-V method. Three deep levels, E1, E2 and E3, have been found near the heterointerface, whose activation energies are 0.17 eV, 0.37 eV and 0.54 eV, respectively. The concentrations of E2 and E3 rapidly decrease when approaching the heterointerface from the InP, indicating that the two levels are located only in the InP substrate. The E1 level, on the other hand, can be found only near the heterointerface. The density of the E1 level is well correlated with the interface charge density which is determined by the C-V analysis. Both of the densities are dependent on the degree of the lattice mismatch between the InGaAs epitaxial layer and the InP substrate.

Low-loss short-wavelength optical waveguides using ZnSe-ZnS strained-layer superlattices

Low‐loss short‐wavelength optical ridge waveguides using ZnSe‐ZnS strained‐layer superlattices (SLS’s) were successfully fabricated on GaAs substrates by low‐pressure metalorganic vapor phase epitaxy. A propagation loss α as low as 0.71 cm−1 was obtained for the SLS waveguide composed of 80 periods of ZnSe(50 A)‐ZnS(50 A) at the 0.633‐μm wavelength TE fundamental mode. Therefore, this waveguide may be suited for optoelectronic integrated circuits composed of II‐VI and III‐V compound semiconductor devices. Furthermore, these waveguides exhibited a large difference in the propagation loss between TE and TM polarizations which may be related to the birefringence for TE and TM polarizations due to the slight anisotropy of the refractive index in the ZnSe‐ZnS superlattice structure. This birefringence effect will be very useful for a polarizing optical device.

High quality ZnSe films grown by low pressure metalorganic vapor phase epitaxy using methylalkyls

High quality ZnSe layers have been successfully grown by low pressure metalorganic vapor phase epitaxy (MOVPE) using methylalkyls, dimethylzinc, and dimethylselenide. Streaks and Kikuchi lines were observed by reflective high‐energy electron diffraction measurements. Also the sharp and strong excitonic emission line due to free exciton and no emissions related to deep levels or residual impurities were observed by photoluminescence measurements. These results show that the ZnSe layers are of good crystalline quality. Furthermore, good selective growth of the ZnSe films on structured substrates was easily achieved by using this low pressure MOVPE technique.

Deep Levels in InP Grown by MOCVD

Deep levels in the undoped InP grown by MOCVD have been investigated by deep level transient spectroscopy (DLTS). Three electron traps MOE1, MOE2, MOE3 have been observed with activation energies of 0.37 eV, 0.53 eV and 0.60 eV, respectively, in the temperature range between 160 K and 380 K. The trap concentrations of these levels were from 1013 cm-13 to 1015 cm-3 for samples with carrier concentrations of (1-6)×10-16 cm-3. The electron capture cross sections (σn) have been directly determined to be 3.1×10-18 cm2 (at 206 K) for MOE1 and 8.8×10-19 cm2 (at 344 K) for MOE3. For the level MOE2, it has been found that the capture cross section is strongly dependent on temperature, i.e., temperature dependence of this cross section is experimentally well-characterized by the relation σn=4.2×10-12 (cm2) exp (-0.38 (eV)/kT), which indicates the multiphonon emission process occurring during an electron capture event. Two deep levels have also been found in the LEC InP substrate material, which are identical to the defects observed in the epitaxial layer.

Growth of ZnSe/ZnS strained‐layer superlattices on Si substrates

The high‐quality ZnSe‐ZnS strained‐layer superlattices (SLSs), as well as the ZnS layers, were successfully grown for the first time on Si substrates. Photoluminescence (PL) spectra of ZnS layers grown on Si showed an intense excitonic‐emission line. In transmission electron microscopy analyses, no misfit dislocations and no moire fringes were observed on the ZnS layer with a thickness of less than about 500 A. We have also characterized ZnSe‐ZnS SLSs grown on Si substrates. By the PL measurements, an intense excitonic‐emission line, and no emissions due to deep levels, were observed. As the ZnSe well‐layer thickness decreased, the peak of the line largely shifted towards the higher‐energy side. This behavior may be related to the quantum size effect. In the temperature dependence of PL intensity, there appeared the thermal quenching process, which may be related to the thermal release of excitons in quantum wells. As the thickness of the ZnSe well‐layer decreased, the activation energy abruptly increased...

Conformal doping for FinFETs and precise controllable shallow doping for planar FET manufacturing by a novel B 2 H 6 /Helium Self-Regulatory Plasma Doping process

A new self-regulatory plasma doping (SRPD) technique with B2H6/helium gas plasma has been successfully developed that provide conformal doping for fins and precise controllable ultra-shallow doping for planar FET. Manufacturing level of process controllability (<1% on dose) of the new SRPD has been realized, and advantage of the SRPD has been verified with FinFETs with metal/high-k gate stack and planar pMOSFETs for the first time. Short channel effect (SCE) improvement for FinFETs is clearly obtained. Dramatically Ion enhancement (+14% Ion at the Ioff of 10-8 A/um vs. ion implant ref.) with SCE suppression for planar pMOSFETs is also realized. This new SRPD will be the excellent compatible doping method for pMOS FinFETs as well as planar pMOSFETs extension for 32nm node and beyond.

Dependence of elastic strain on thickness for ZnSe films grown on lattice‐mismatched materials

We present a new approach for calculation of the dependence of elastic strain on layer thickness concerning ZnSe films grown on GaAs and on ZnS. The basic concept involved in our model is that the interfacial misfit dislocations are generated only when the areal strain energy density exceeds an energy barrier. It is found that the elastic strain calculated by this model is quite in agreement with experimental results for the ZnSe/GaAs system with the energy barrier of 79 erg/cm2. To compare the theory with experiments, the difference of thermal expansion coefficient between the epitaxial layer and the substrate must be taken into consideration. Applications of the model to other systems are also discussed.

Conformal doping mechanism for fin field effect transistors by self-regulatory plasma doping with AsH3 plasma diluted with He

Key parameters for achieving n-type conformal doping desirable for source/drain extension regions of Si n-channel fin field effect transistors (FinFETs) have been determined for self-regulatory plasma doping using an AsH3 plasma diluted with He. Two-dimensional scanning spreading resistance microscopy revealed that this technique is advantageous for conformal doping of fin structures. An excellent resistivity conformality was obtained with the ratio of the resistivity of fin sidewall to that of the fin top surface being 0.85. A high total gas flow rate and a high AsH3 concentration were found to be important conditions for realizing conformal doping. The results revealed that a short gas residence time and high molar concentrations of AsH3 and He in the process chamber are essential physical parameters for realizing large amounts of dopant species with finite decomposition times. When these conditions are realized, a sufficiently large amount of As is supplied to both the top surface and the sidewall so t...

Raman scattering in (AlxGa1−x)0.51In0.49P quaternary alloys

We report a Raman study of the phonon mode of (AlxGa1−x)0.51In0.49P quaternary alloys lattice matched to GaAs over the whole range of compositions. From the composition dependence of spectra it has been confirmed that the three‐mode behavior of the alloy corresponding to the three binary compositions: AlP‐, GaP‐, and InP‐like phonon modes may occur.