Xuliang Zhou

Exchange anisotropy of epitaxial Fe/MnPd bilayers

The anisotropy contributions in epitaxial Fe/MnPd bilayers were analyzed in this study. It was found that due to ferromagnetic–antiferromagnetic interfacial exchange coupling, large uniaxial and cubic anisotropy contributions are also induced, in addition to the unidirectional anisotropy. These contributions play an essential role in the magnetization reversal process of the system, in which unusual reversal processes were found upon some fields orientations.

Ridge InGaAs/InP multi-quantum-well selective growth in nanoscale trenches on Si (001) substrate

Metal organic chemical vapor deposition of InGaAs/InP multi-quantum-well in nanoscale V-grooved trenches on Si (001) substrate was studied using the aspect ratio trapping method. A high quality GaAs/InP buffer layer with two convex {111} B facets was selectively grown to promote the highly uniform, single-crystal ridge InP/InGaAs multi-quantum-well structure growth. Material quality was confirmed by transmission electron microscopy and room temperature micro-photoluminescence measurements. This approach shows great promise for the fabrication of photonics devices and nanolasers on Si substrate.

High-power InGaAs/GaAs quantum-well laser with enhanced broad spectrum of stimulated emission

We report the demonstration of an InGaAs/GaAs quantum well (QW) broadband stimulated emission laser with a structure that integrated a GaAs tunnel junction with two QW active regions. The laser exhibits ultrabroad lasing spectral coverage of ∼51 nm at a center wavelength of 1060 nm with a total emission power of 790 mW, corresponding to a high average spectral power density of 15.5 mW/nm, under pulsed current conditions. Compared to traditional lasers, this laser with an asymmetric separate-confinement heterostructure shows broader lasing bandwidth and higher spectral power density.

1.06-μm InGaAs/GaAs multiple-quantum-well optical thyristor lasers with a PiNiN structure.

InGaAs/GaAs multiple quantum well (MQW)-depleted optical thyristor lasers operating at 1.06 μm with a waveguide-type PiNiN structure is presented for the first time. The optical thyristor lasers clearly show nonlinear S-shaped current-voltage and lasing characteristics. The measured switching voltage and current are 5 V and 1 mA, respectively. The holding voltage and current are 2.6 V and 3.6 mA, respectively. A relatively high output light power of 30 mW per facet at room temperature is achieved. The lasing wavelength is 1.055 μm at a bias current of 80 mA at 25 °C.

A Directional-Emission 1060-nm GaAs/InGaAs Microcylinder Laser

A GaAs/InGaAs microcylinder laser in diameter of 15 μm connected with a 2-μm wide output waveguide is fabricated using standard photolithography and inductively coupled plasma etching technique. With the output waveguide, we realize the directional emission with the pulsed lasing operation wavelength of 1060 nm at room temperature. The maximum output power is ~6 μW and the minimum threshold current is 2 mA, which is comparatively low compared with previous reported GaAs material microlasers. A single mode operation is achieved near threshold current at the wavelength of 1060 nm. Mode characteristics are calculated and analyzed by 2-D finite-difference time-domain simulation. The small volume, low threshold current, and low energy consumption make the GaAs/InGaAs microcylinder laser we presented a promising light source for optical interconnection on chip.

An intermediate-band-assisted avalanche multiplication in InAs/InGaAs quantum dots-in-well infrared photodetector

The avalanche multiplication of photocurrent in InAs/InGaAs quantum dot infrared photodetectors (QDIPs) has been observed in the temperature range from 20 to 80 K. The avalanche onset voltage Vth, being larger than 1.2 V at T 60 K. This singularity of Vth indicates that intermediate-band-assisted avalanche multiplication is achieved in our dots-in-well structure, which benefits from the abrupt change of the electron occupation of the intermediate band at a temperature of approximately 55 K. The remarkable reduction of Vth for QDIP is a useful enhancement in the infrared detector’s performance.

The Comparison of Current Ratio

This paper mainly describes the comparison of I_ON/I_OFF ratio and mobility between SiGe substrate and GaAs substrate In_0.23Ga_0.77As channel MOSFETs grown by metalorganic chemical vapor deposition. In order to make the comparison more reasonable, we choose the same size (Lg = 10 μm) for both the SiGe substrate and GaAs substrate MOSFETs. As for the SiGe substrate MOSFETs, its highest ON-current to the lowest OFF-current (I_ON/I_OFF) ratio is less than 1×103, while that of GaAs substrate MOSFETs are up to 4×10⁴ (both at a gate bias of 3 V). Due to the Ge diffusion into the InGaAs channel, it will make the intrinsic channel become an n-type doped semiconductor and then influence the pinchoff characteristics. The maximum effective mobility of SiGe substrate MOSFETs is 1800 cm²/V · s and that of GaAs substrate MOSFETs is up to 2090 cm2/V · s. The main reason for the higher mobility of GaAs substrate MOSFETs is maybe due to its smaller density interface trap density Dit and undoped InGaAs channel. Through comparing the performance, particularly the I_ON/I_OFF ratio and mobility between SiGe substrate and GaAs substrate MOSFETs, we aim to find out some feasible methods to improve the performance of InGaAs channel MOSFETs on SiGe substrate.

I_{\mathrm{\scriptscriptstyle ON}}/I_{\mathrm{\scriptscriptstyle OFF}}

We report high-mobility In0.23Ga0.77As channel MOSFETs grown on Ge/Si virtual substrate by metal-organic chemical vapor deposition for the first time. Through a low-temperature GaAs nucleation layer on Ge surface, a high-quality III-V MOSFET structure is obtained, with its etch pit density of 1.5 × 105 cm-2. The maximum effective mobility is up to 1880 cm2/Vs, extracted by the split C-V method. The highest ON-current to the lowest OFF-current (ION/IOFF) ratio of ~2000 has been obtained. The 8-μm channel-length devices exhibit a drain current of 60 mA/mm and a peak extrinsic transconductance of 20 mS/mm. These results indicate that the high-mobility III-V nMOSFETs on Si substrate can be realized and even used to act as nMOSFETs for the fabrication of future CMOS.

and Mobility Between SiGe Substrate and GaAs Substrate In 0.23 Ga 0.77 As Channel MOSFETs

We demonstrate high-performance In0.23 Ga0.77 As channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with high on-current to off-current (Ion/Ioff) ratio grown on semi-insulating GaAs wafers by metal-organic chemical vapor deposition (MOCVD). The 2 μm channel-length devices exhibit a peak extrinsic transconductance of 150 mS/mm and a drain current up to 500 mA/mm. The maximum effective mobility is 1680 cm2/Vs extracted by the split C-V method. Furthermore, the Ion/Ioff ratio is significantly improved from approximately 4.5 × 103 up to approximately 4.32 × 104 by controlling the etch thickness of In0.49 Ga0.51 P. The high drain current and high Ion/Ioff ratio of the In0.23 Ga0.77 As channel MOSFETs are achieved due to the high effective mobility and the low gate leakage current density.

High-Mobility In 0.23 Ga 0.77 As Channel MOSFETs Grown on Ge/Si Virtual Substrate by MOCVD

The effect of the additional confining potentials on ferromagnetism in III–V digital ferromagnetic heterostructures has been studied by ab initio calculations in combination with pseudopotential plane-wave method. The electronic and magnetic properties are shown as a function of the thickness of AlAs layers in the GaAs∕AlAs digital ferromagnetic heterostructures. It is found that all the structures show ferromagnetic alignment for the most favored configuration and their electronic structures are half metallicity. The exchange coupling constants N0β are estimated by using the spin splitting of the valence band. It is also shown that the charge density and the strong spin polarization are concentrated mostly on the magnetic layers for all structures. Furthermore, the hole distributions are analyzed in terms of their orbital projected density of states. The concentration of confined hole within the magnetic layer increases with increasing the additional potentials, which is responsible for the enhancement o...