Series connected InGaAs using GaAsSb tunnel junction

A Laser power converter (LPC) cell targeting 0.74 eV has been grown on an InP substrate using two lattice-matched GaInAs p/n junctions vertically stacked with a tunnel diode, resulting in double the output voltage and half of the output current. Historically, multi-junction devices like this have typically used Zinc doped p+GaInAs in the tunnel junction. However, this can be difficult to grow reliably by MOCVD and Zn diffusion can lead to lower tunnel diode performance. In this work, MicroLink demonstrates a multijunction GaInAs cell using a novel p+GaAsSb/n+InP tunnel junction from diffusion stable C doped p+GaAsSb. These LPC cells are also grown inverted and then processed using substrate etch back into thin film foils for added performance. This thin film LPC cell would improve thermal conductivity by a factor of 43 and specific power by a factor of 4.2 compared to series interconnected upright LPC designs.