H.J. Lee

Very small temperature-dependent band-gap energy in TlInGaAs/InP double heterostructures grown by gas-source molecular-beam epitaxy

TlInGaAs/InP double heterostructures (DHs) were grown on (100) InP substrates by gas-source molecular-beam epitaxy. Almost no occurrence of Tl interdiffusion at the InP/TlInGaAs heterointerface was confirmed. The photoluminescence (PL) intensity for the DH was approximately ten times stronger than that of the single heterostructure. The PL peak energy and its variation with temperature for the TlInGaAs/InP DH decreased with increasing Tl composition. For the DH with a Tl composition of 13%, the PL peak energy varied only slightly with temperature (0.03 meV/K). This value corresponds to a wavelength variation of 0.04 nm/K and is much smaller than that of the lasing wavelength of InGaAsP/InP distributed feedback laser diodes (0.1 nm/K).

Gas Source Molecular Beam Epitaxy Growth of TlInGaAs Layers on GaAs Substrates

New alloy semiconductor TlInGaAsN/AlGaAs heterostructures for fabricating 1.3–1.55 µm wavelength laser diodes with temperature-stable threshold current and temperature-stable lasing wavelength are proposed. TlInGaAs/GaAs and InGaAs/GaAs double-hetero (DH)-, multi-hetero (MD)- and single-quantum-well (SQW) structures were grown on GaAs substrates by gas source molecular beam epitaxy. Incorporation of Tl into TlInGaAs was confirmed up to 9% with reflection high-energy electron diffraction intensity oscillation. Red shift of the photoluminescence peak energy was also observed for TlInGaAs/GaAs DH, MH and SQW samples, which agrees with the incorporation of Tl.

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.

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.

Temperature-Stable Wavelength TlInGaAs/InP Double Heterostructure Light-Emitting Diodes Grown by Gas Source Molecular Beam Epitaxy

TlInGaAs/InP double heterostructure light-emitting diodes were grown on (100) InP substrates by gas source molecular beam epitaxy. The Tl composition was 6%. They were operated at up to 340°C with a wavelength around 1.58 µm. Very small temperature dependence of the electroluminescence peak energy (-0.09 meV/K) was observed, which is similar to the temperature dependence of the photoluminescence peak energy.

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.

Temperature stable wavelength TlInGaAs/InP DH LEDs grown by gas source MBE

TlInGaAs/InP double heterostructure (DH) light emitting diodes (LEDs) were grown on [100] InP substrates by gas source molecular beam epitaxy. The Tl composition was 6%. They were operated up to 340 K in the wavelength range of 1.58 /spl mu/m. Very small temperature variation in the electroluminescence (EL) peak energy (-0.09 meV/K) was observed, similar to the temperature variation of photoluminescence (PL) peak energy.

Gas source MBE growth of TlInGaAs layers on GaAs substrates

New alloy semiconductor heterostructures TlInGaAsN/AlGaAs are proposed to fabricate 1.3-1.55 /spl mu/m wavelength laser diodes with temperature-stable threshold currents and temperature-stable lasing wavelengths. TlInGaAs/GaAs and InGaAs/GaAs double-hetero (DH) and multi-hetero (HD) structures were grown on GaAs substrates by gas source molecular-beam epitaxy (MBE). Incorporation of Tl into TlInGaAs was confirmed up to 9% with reflection high energy electron diffraction (RHEED) intensity oscillation. Red shift of the photoluminescence (PL) peak energy was also observed for TlInGaAs/GaAs DW and MH samples, which agrees with the incorporation of Tl.