Charge transfer characteristics of the long wavelength semiconductor laser structures, containing quantum dot layers (QDs), were investigated by means of temperature dependent current-voltage and electroluminescence measurements over InAs/InP, and InAs/GaAs based p-i-n structures. In InAs/InP elongated QDs (QDashes) structure, injected carriers were tunneled from the quantum well into QDashes through a thin barrier and subsequently recombined within QDashes. Meanwhile, for InAs/GaAs structure, tunneling kind transport was exhibited in both forward and reverse bias voltage directions. The onset of light took place when the forward bias exceeded 1.3 V (3 V) for InAs/InP (InAs/GaAs) p-i-n structure through electroluminescence measurements. The peak value of emitted laser light for InAs/InP QDashes and InAs/GaAs QDs occurred in 1.55 μm and 1.3 μm, respectively.
III-V semiconductor low dimensional structures are attractive for optoelectronic devices, including laser diodes and infrared photodetectors [
Therefore, the charge transport properties are essential for the dynamic of a high-speed semiconductor laser [
State of the art device quality InAs/InP-based QDashes―elongated quantum dots- devices were grown by gas source molecular beam epitaxy on S-doped (100) InP wafers. The schematic structure was shown in the inset of
SEM images of the long wavelength laser heterostructure in the p-i-n diode were presented in
To elucidate the carrier conduction mechanism(s), a general diode equation is fitted, and the results are investigated in terms of activation energy (EA) of the saturation current (I0) and temperature dependence of the exponential factor (A) by performing temperature dependent current density-voltage measurement. In this context, the current density-voltage relation in the forward directions is expressed as [
where V is applied voltage. Dark saturation current density is given by
with
where k is Boltzmann’s constant, T is the absolute temperature in Kelvin, q is electron charge, and n is ideality factor.
In reverse direction, reverse current density-reverse bias followed the expression,
with
where Vbi is built-in voltage, VR is applied voltage in reverse bias, b is temperature independent exponent, and Jrev,0(T) is dark saturation current density in reverse bias, and EA,rev is reverse bias activation energy.
For QDashes based p-i-n laser heterostructure, the forward J-V characteristic manifested two distinct behaviors depending on the bias range (VF < 0.2 V and 0.2 < VF < 0.6 V). From the slopes of Arrhenius plots of ln J0vs. T−1 and Avs. T−1 variations, EA was deduced as 0.4 eV, and A was independent of temperature (
Similarly, InAs/GaAs Quantum Dot based p-i-n structure was analyzed (
Furthermore, when the junctions entered the space charge limited region (VF > 1 V for InAs/InP Quantum dash and VF > 2 V for InAs/GaAs Quantum Dot), the laser light was observed (
Long wavelength laser diodes in the p-i-n structure were investigated by temperature dependent current density-voltage measurements. Tunneling kind carrier conduction mechanism was identified for InAs/GaAs-based p-i-n structure for whole bias voltages, whereas transition of tunneling type to recombination/gen- eration kind carrier conduction was discerned in InAs/InP-based p-i-n laser diode. As to the EL measurements, laser light emerged for both structures, peaking at 1.55 µm and 1.3 µm, respectively.
The authors are grateful to Laboratory for Photonics and Nanostructures (LPN), CNRS for the sample production and Prof. Dr. Abderrahim Ramdaneand his co- workers.
Kuruoğlu, N.A., Özdemir, O. and Bozkurt, K. (2017) Investigation of Carrier Conduction Mechanism over InAs/InP Quantum Dashes and InAs/ GaAs Quantum Dots Based p-i-n Laser Heterostructures. Journal of Materials Science and Chemical Engineering, 5, 1-9. https://doi.org/10.4236/msce.2017.59001