A. Fujiwara

Temperature stability of the refractive index and the direct bandedge in TlInGaAs quaternary alloys

TlInGaAs quaternary alloy layers were grown on InP substrates by gas-source molecular-beam epitaxy. Refractive index dispersions were determined at the temperature range of 300–340 K in the photon-energy region below and a little above the direct bandedge E0 by the optical reflectance measurements. The temperature dependence of the refractive index was analyzed with the first-order Sellmeier equation. The temperature dependence of the E0 edge was also determined by the absorption measurements. It was found that the temperature coefficients of both refractive index and E0 edge of TlInGaAs are much smaller than those for InGaAs. These results facilitate the fabrication of the temperature-stable-wavelength optoelectronic devices using this alloy system.

Observation of Small Temperature Variation of Longitudinal-Mode Peak Wavelength in TlInGaAs/InP Laser Diodes

To fabricate temperature-insensitive wavelength laser diodes (LDs), which are important in the wavelength division multiplexing optical fiber communication system, we have studied TlInGaAs/InP heterostructures. TlInGaAs/InP metal-stripe LDs were fabricated with gas source molecular-beam epitaxy. Current-injection pulsed-laser operation was obtained up to 310 K. Threshold current density and lasing wavelength at room temperature were 7 kA/cm2 and 1660 nm, respectively. The observed temperature variation of the longitudinal-mode peak wavelength was as small as 0.06 nm/K. This value is much smaller than that observed for distributed feed-back LDs (0.1 nm/K). This is considered to result from the addition of Tl into the LD active layer.

Reduced temperature dependence of refractive-index in TlInGaAs quaternary alloys grown on InP substrates

Refractive-index dispersion for the TlInGaAs quaternary alloys, grown on (100) InP substrates by gas-source molecular-beam epitaxy, has been measured at temperatures from 290 to 350 K in the photon-energy range of 1.2–2.0 eV by using spectroscopic ellipsometry. The temperature coefficient of the refractive-index decreases with increasing Tl composition. The result corresponds to the already reported reduced temperature dependence of the band-gap energy for the TlInGaAs because of the alloy of semiconductor InGaAs and semimetal TlAs. The result also agrees with the recently reported small temperature-variation of the lasing-wavelength for the TlInGaAs/InP laser diodes.

High-Frequency Heterodyned Detection of Picosecond Accumulated Photon Echoes

Highly sensitive detection of accumulated photon echoes was achieved by means of a high-frequency heterodyned method using a mode-locked CW dye laser. Experimental results on the modulation frequency dependence of the echo signal strength and also the excitation wavelength dependence of the echo decay curves in Nd:silicate glass are presented.

Current Injection Laser Oscillation in TlInGaAs/GaAs Double Quantum Well Diodes with InGaP Cladding Layers

TlInGaAsN/AlGaAs heterostructures were proposed for use in the fabrication of temperature-stable lasing wavelength and threshold current laser diodes. As a first step, we grew TlInGaAs/GaAs quantum well (QW) structures on GaAs(100) substrates and demonstrated an electroluminescence (EL) emission of up to 300 K. Compared with InGaAs/GaAs QWs, we confirmed that the temperature variation of the EL peak energy was decreased by the addition of Tl into InGaAs. We also demonstrated the pulsed current injection laser oscillation in the TlInGaAs/GaAs double QW laser diodes with InGaP cladding layers up to 176 K.

Temperature-dependence of lasing spectrum for TlInGaAs/InP DH laser diodes and 77K CW operation

In order to fabricate the temperature-insensitive wavelength laser diodes (LDs), which are important in the WDM optical fiber communication system, we have studied the TlInGaAs/InP heterostructures. TlInGaAs/InP metal-stripe LDs were fabricated with gas source MBE. Current injection pulsed laser operation was obtained up to 310K. Threshold current density and lasing wavelength at room temperature were 7 kA/cm/sup 2/ and 1660 nm, respectively. We have observed the small temperature variation of the peak wavelength of 0.06nm/K at narrow temperature range, while at wide temperature range it was about 0.3 nm/K. Both values are smaller than those for InGaAsP/InP DFB LDs and Fabry-Perot (FP) LDs, respectively. CW operation was also obtained at 77K with a threshold current density of 0.25 kA/cm.

Gas source MBE growth of TlInGaAs/InP laser diodes and their first successful room temperature operation

Summary form only given. Wavelength division multiplexing (WDM) technology is very important for optical fiber communication systems to increase transport capacity. However, one of the problems encountered when using InGaAsP/InP laser diodes (LDs) is that the lasing wavelength fluctuates with ambient temperature variation mainly due to the temperature dependence of the bandgap energy. To overcome this problem, we proposed TlInGaAs(P) as new III-V semiconductors showing temperature-independent bandgap energy for the possible application to the temperature-stable lasing wavelength LDs. We have already succeeded in the growth of TlInGaAs/InP double-hetero (DH) structures and obtained the very small temperature variation of the photoluminescence (PL) and electroluminescence (EL) peak energies. In this paper, we will report the gas source MBE growth of TlInGaAs/InP LD wafers and their first successful laser operation.

Room temperature operation of TlInGaAs/InP DH laser diodes

Tl-containing III-V semiconductors are expected to fabricate the temperature-insensitive wavelength laser diodes (LDs), which are important to effectively use light wavelength sources, especially in the WDM optical fiber communication systems. TlInGaAs/InP DH structures were grown by gas source MBE. Small temperature variation of electroluminescence emission peak wavelength was observed. TlInGaAs/InP DH LDs were fabricated and observed the first successful laser operation at room temperature. The threshold current density was about 5 kA/cm/sup 2/ under pulsed operation and the T/sub 0/ value was 85 K.

Quinary TlGaInNAs DQW Structures: Effect of Growth Temperature and Growth Rate on Tl Incorporation

TIGalnNAs-based DQW structures grown at various growth parameters were studied by secondary ion mass spectroscopy (SIMS). Enhanced Tl incorporation could be obtained using TlGaNAs barriers. A direct relationship between the Tl incorporation and N composition is clearly established by the analysis of the effect of growth temperature, growth rate, ECR power and nitrogen flow rate. The Tl incorporation increased with the increase of Tl flux in the case of DQW structures with TlGaAs barriers. In the case of DQW structures with TIGaNAs barriers, the Tl incorporation reached saturation at some Tl flux, indicating the N enhanced higher Tl incorporation.

MBE Growth of TlInGaAs/TlInP/InP SCH LDs and Their Laser Operation

TlInGaAs/TllnP/InP separate confinement heterostructures (SCHs) were grown by gas-source molecular-beam epitaxy and metal stripe laser diodes (LDs) were fabricated. Temperature variation of electroluminescence peak wavelength was as small as 0.06 nm/K due to the reduced temperature variation of band gap energy of TlInGaAs. Pulsed laser operation was achieved at 77 K - 297 K. Threshold current density for the TlInGaAs/TlInP/InP SCH LD (0.6 kA/cm2 at 77 K) was smaller than that for the TlInGaAs/InP double heterostructure LD (0.8 kA/cm2 at 77 K), which is due to the increased refractive index for TlInP and the improved optical confinement. Temperature variation of main peak wavelength in the lasing spectra was as small as 0.07 nm/K, which is much smaller than those for the InGaAsP/InP Fabry-Perot LDs (0.4 nm/K) and distributed feed-back LDs (0.1 nm/K)