Gas Source MBE Growth and Characterization of TlInGaAs/InP DH Structures for Temperature-independent Wavelength LD Appli
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Gas Source MBE Growth and Characterization of TlInGaAs/InP DH Structures for Temperature-independent Wavelength LD Application Hajime Asahi, Hwe-Jae Lee, Akiko Mizobata, Kenta Konishi, Osamu Maeda and Kumiko Asami The Institute of Scientific and Industrial Research, Osaka University 8-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan ABSTRACT TlInGaAs/InP double-hetero (DH) structures were grown on (100) InP substrates by gas source MBE. The photoluminescence (PL) peak energy variation with temperature 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). TlInGaAs/InP light emitting diodes with 6% Tl composition were fabricated and the small temperature variation of the electroluminescence peak energy (-0.09 meV/K) was observed at the wavelength around 1.58 µm. The results are promising to realize the temperature-independent wavelength laser diodes, which are important in the wavelength division multiplexing (WDM) optical fiber communication systems. INTRODUCTION Wavelength division multiplexing (WDM) technology is very important for optical fiber communication systems to drastically increase transport capacity. However, one of the problems encountered when using InGaAsP/InP laser diodes (LDs) in WDM systems is that the lasing wavelength fluctuates with ambient temperature variation mainly due to the temperature dependence of the bandgap energy. Therefore, LDs in WDM systems are equipped with Peltier elements to stabilize LD temperature. To solve this problem, the use of temperature-independent bandgap semiconductors as an active layer of LDs was proposed [1]. We have proposed III-V quaternary semiconductors, TlInGaP (Thallium Indium Gallium Phosphide) [2, 3] and TlInGaAs (Thallium Indium Gallium Arsenide) [3] as shown in figure 1. TlInGaP and TlInGaAs can be lattice-matched to InP, and cover the bandgap energies corresponding to the 1 µm wavelength range. Furthermore, we pointed out that TlInGaP and TlInGaAs are expected to show the temperature-independent bandgap energy at certain compositions because it is an alloy of semiconductor, InGaP or InGaAs, and semimetal, TlP or TlAs, similar to HgCdTe. CdTe is a semiconductor and HgTe is a semimetal. Temperature-independent bandgap energy was observed for HgCdTe at a Hg composition of 0.48 [4]. Therefore, the LDs fabricated using TlInGaP or TlInGaAs have the potential to operate without changing wavelength irrespective of
H9.27.1
Bandgap Energy (eV)
2.0 1.5 1.0
AlP GaP GaAs 1.2 ~ 1.6 µm
0.5
AlSb InP
1
GaSb InAs
0.0 -0.5
InSb 2 5
TlP
-1.0 0.5
0.5
AlAs
Wavelength (µm)
2.5
direct gap indirect gap lattice-match
TlAs 0.55 0.6 Lattice Constant (nm)
0.65
Figure 1. Bandgap energy vs. lattice constant relationship for TlInGaP and TlInGaAs.
ambient temperature variation [2, 3]. We have suc
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