Long Wavelength GaInAsP/InP Laser with n-n Contacts Using AlAs/InP Hole Injecting Tunnel Junction

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Abstract
We demonstrate InP-based long-wavelength lasers with an AlAs/InP tunnel junction prepared in the upper cladding of a standard laser structure to convert electron current supplied by the upper n-electrode to hole current. A carbon auto-doped AlAs layer was employed as a heavy p-type layer required for the tunnel junction. The tunnel junction diode showed a small electrical resistance under a reverse-biased condition. In addition, a negative differential resistance characteristic was clearly observed under a forward-biased condition. The introduction of such a tunnel junction can eliminate the p-electrode which normally exhibits a high resistivity in InP-based lasers. In the fabricated lasers with tunnel junctions, it was observed that the tunnel junction can enhance lateral current spreading due to low resistance in the n-layer. The proposed structure for hole sources may be useful for reducing the resistance and homogenizing the carriers in the active region of long-wavelength vertical-cavity surface-emitting lasers (VCSEL).