In Figure 2, we also plotted the amplitudes of three different ph

In Figure 2, we also plotted the amplitudes of three different photocurrent (PC) oscillations versus the excitation wavelength. It is clear that the maximum amplitude of the oscillations is reached when the excitation wavelength is in resonance with the GaInNAs bandgap, confirming that they are associated

with photogenerated carriers within the GaInNAs QWs. Figure 2 Comparison between spectral photoresponse of AsN2604 and amplitude of the first three selleck oscillations versus excitation wavelength. Further evidence for the instabilities in PC being associated with photogenerated carriers in the QWs comes from the observation of PL oscillations when the device bias is varied [27]. In this experiment, the PL signal was integrated over all the GaInNAs optical transition. It is clear from

Figure 3 that the PL oscillations are out of phase with the PC oscillations and occur at the same applied bias voltages. This is because when the oscillating component of the non-radiative current goes through a minimum, the radiative current will increase leading to the observed maximum in PL. Figure 3 I – V and integrated PL versus applied voltage for AsN2604 at T  = 100 K. The derivatives of the curves are plotted in the inset. The first derivatives of the I-V curves for VN1585, AsN3134 and AsN3138 are shown in Figure 4. The samples with 10 QWs, VN1585 and AsN3134 have 10 clear oscillations. In AsN3138 with 20 QWs, there are 18 distinct peaks in the PC. We were not able to observe the two further expected peaks in this sample because the diode entered the breakdown region. Figure 4 First derivative of AsN3134, AsN3138 and VN1585 I – V curves at T  = 15 K, shifted for clarity. The origin of these oscillations is to be searched into the different confinement of electrons and holes inside the GaInNAs QWs. Table 2 lists the CB offset Interleukin-3 receptor ΔE C and the valence band (VB) offset

ΔE V, calculated using the band anti-crossing model and a 8-band k.p Hamiltonian [30]. ΔE V is considerably smaller than ΔE C for all samples, leading to good electron confinement but poor hole confinement. Because of the QW bidimensional structure, carriers will lay in a discrete number of subband energy levels, whose number will depend upon the thickness of the QW. In our samples at T = 100 K, up to three levels are allowed. Their energies (measured from the band edges) are also listed in Table 2. It can be noticed that some of them are so close to the band edges (few meV) that it will be very easy for the carriers there to escape into the surrounding barriers. Table 2 Electron and hole confinement energies and band offsets Sample ΔE C (meV) Electron confinement energies (meV) ΔE V (meV) Hole confinement energies (meV) AsN2604 (for the 3.

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