Jyh-Shyang Wang

Room-temperature 2.2-/spl mu/m InAs-InGaAs-InP highly strained multiquantum-well lasers grown by gas-source molecular beam epitaxy

We report the fabrication and performances of 2.2-/spl mu/m InAs-InGaAs-InP highly strained multiple-quantum-well (MQW) lasers grown by gas-source molecular beam epitaxy. The lasers operated at room temperature demonstrate a threshold current density of 900 A/cm/sup 2/ a maximum external quantum efficiency of 28%, and a maximum output power exceeding 60 mW per facet. To the best of our knowledge, this is the longest room-temperature emission wavelength reported for lasers grown on InP substrates to date. The effect of strain compensation on the quality of the InAs-In/sub x/Ga/sub 1-x/As MQWs was also studied using double crystal X-ray diffractometry and photoluminescence techniques. The experimental results reveal that there is no significant difference on the epilayer quality of the samples with strain compensation. However, the group V stable surface growth condition is indeed better than the group III stable surface growth condition on the epilayer quality.

Growth of InAsN/InGaAs(P) quantum wells on InP by gas source molecular beam epitaxy

The growth of InAsN/InGaAs(P) quantum wells (QWs) on InP substrates by gas-source molecular-beam epitaxy and a rf plasma nitrogen source is reported for the first time. The double crystal x-ray diffraction satellite peaks of the InAsN/InGaAsP multiple quantum well (MQW) samples are sharper than those of the pure InAs/InGaAsP MQW samples, showing that a flatter heterointerface is achieved due to the smaller lattice mismatch. However, broadening of the satellite peaks and degradation of the photoluminescence (PL) intensity due to the increase of the nitrogen composition in these InAsN/InGaAsP MQWs suggest the existence of defects introduced by the small diameter nitrogen atoms located on arsenic sites. The PL result also shows that the peak energy decreases as the nitrogen composition increases. The estimated transition energy shrinkage coefficient is −31 meV/at. % nitrogen. The largest nitrogen composition obtained in this study is 5.9%, and its 10 K PL peak wavelength is ∼2.6 μm (480 meV). The effects of ...

Growth and postgrowth rapid thermal annealing of InAsN/InGaAs single quantum well on InP grown by gas source molecular beam epitaxy

InAsN/InGaAs single quantum wells (SQWs) with different nitrogen concentration have been successfully grown on InP substrates by gas source molecular beam epitaxy used rf plasma nitrogen source. Photoluminescence (PL) results of the as-grown samples show red-shifted PL peak energy and rapidly degraded intensity as the nitrogen concentration increases. The roughly estimated maximum nitrogen mole fraction in these samples is 0.4%. Both the PL intensity and linewith of these InAsN/InGaAs SQWs were significantly improved after postgrowth rapid thermal annealing with the optimum temperature at 525–550 °C for samples with different nitrogen content. The improvement on 10 K PL intensity can be as high as 230 times, and the room temperature PL intensities of the annealed InAsN SQWs have been comparable to those of InAs SQWs used for laser diodes. Quantum well intermixing (QWI) induced blue-shifted PL spectra were also observed in these samples. The QWI threshold temperature decreases as the nitrogen concentration...

Dielectric studies of Zn1−xMnxSe epilayers

We report on the dielectric properties of Zn1−xMnxSe(0⩽x⩽0.78) epilayers, by capacitance and dissipation factor measurements at temperature 5 K<T<475 K and frequency 20 Hz<f<100 kHz. A Debye-like relaxational contribution to the dielectric response is observed, which requires the presence of charge redistribution. The relaxation is found to be a thermally activated process, and the activation energies obtained from the dissipation factor and capacitance are in good agreement. The capacitance is found to increase with a decrease in test frequency. From our results it is established that the dielectric response is caused by carrier hopping among structural defects. A monotonic variation is found in the relationship between the activation energy and the Mn concentration. This monotonic variation is interpreted in terms of the four-center model, in which the number of Mn atoms appearing in the nearest-neighbor sites of the defect can have four possible configurations. The measured defect behavior reflects the...

Optical properties of as-grown and annealed InAs(N)/InGaAsP strained multiple quantum wells

Optical and structural properties of as-grown and annealed InAs(N)/InGaAsP strained multiple quantum-well (MQW) structures grown by gas source molecular-beam epitaxy are investigated by photoluminescence (PL), double crystal x-ray diffraction, and photoconductivity spectroscopies. Properties of the as-grown and annealed MQW’s are studied and those of the InAs/InGaAsP MQW (C821) and the InAsN/InGaAsP MQW with the lowest nitrogen contents N=1.1% in the well (C822) are compared. For the C821 InAs/InGaAsP MQW with a very large total strain, a low energy shoulder, possibly induced by defects or impurities, can be seen in the low temperature PL spectrum, and a large density of nonradiative recombination centers is found. For nitrogen-containing MQW’s, the PL full width at half maximum and PL peak evolutions with increasing annealing temperature are influenced by the alloy inhomogeneities. The initial redshift of the PL peak after rapid thermal annealing means that the luminescence is dominated by As-rich region...

Growth and characterization of InAsN alloys

The growth of InAsN alloys on InP and InAs substrates by using gas source molecular beam epitaxy (GSMBE) and RF plasma nitrogen source is reported. The samples grown on InP substrates were 3-nm-thick InAsN quantum wells (QWs). The nitrogen composition determined using double crystal X-ray diffractometer (DXRD) is linearly dependent on the nitrogen flow rate. The incorporation of nitrogen decreases the PL emission energy of the QWs. Increase the nitrogen composition by one-percent causes a red-shift energy of 31 meV. The highest nitrogen composition obtained in this study is 5.9%, acid its 10 K PL peak wavelength is as long as 2.6 /spl mu/m (480 meV). The DXRD results also indicate that the satellite peak linewidths of InAsN QWs are narrower than those of InAs QW, which means that the incorporation of nitrogen can sharpen the interfaces of QWs because it results in smaller lattice mismatch. However, increase nitrogen composition also degrades both the DXRD linewidths and the PL intensity. It suggests the existence of the residual strain or immiscibility introduced by the small diameter nitrogen atoms seated on arsenic sites. For InAsN grown on InAs substrates, the incorporation efficiency of nitrogen is much lower than that of InAsN grown on InP substrates. Compressive strain in InAsN on InP substrate could enhance the incorporation of nitrogen.

Subpicosecond time-resolved Raman studies of ballistic electron transport in InP

Electron ballistic transport and in a InP-based p-i-n nanostructure under the application of an electric field have been studied by time-resolved Raman spectroscopy at T equals 300 K. The time-evolution of electron distribution, electron drift velocity has been directly measured with subpicosecond time resolution. Our experimental results show that, for a photoexcited electron-hole pair density of n is congruent to 5 X 1016 cm-3, electrons travel quasi- ballistically--electron drift velocity increases linearly with time, during the first 150 fs. After 150 fs it increases sublinearly until reaching the peak value at about 300 fs. The electron drift velocity then decreases to its steady-state value.

Direct observation of electron velocity overshoot in an InP p-i-n nanostructure semiconductor: A subpicosecond Raman probe

We have studied transient electron transport in an InP p-i-n nanostructure semiconductor by subpicosecond Raman spectroscopy at T equals 300 K. Both the non-equilibrium electron distribution and electron drift velocity in the regime of electron velocity overshoot have been directly measured. It is demonstrated that electron drift velocity in an InP p-i-n nanostructure is significantly larger than that in a GaAs p-i-n nanostructure sample, as a result of the larger central to satellite valley energy separation in InP.