Symmetric triangular-barrier optoelectronic switch (S-TOPS) by gas source MBE

We report a novel optical functional device, a symmetric triangular-barrier optoelectronic switch (S-TOPS), which consists of a symmetric n⁺-i-δp⁺-i-n⁺ structure of In_0.53Ga_0.47As, grown by a gas source molecular beam epitaxy (GSMBE). We fabricated the S-TOPS by changing the sheet-carrier concentration of the δp⁺ gate layer to introduce an avalanche multiplication for positive feedback in the operation. In the current vs. voltage characteristics of the S-TOPS under illumination of 1.55 μm wavelength light, we successfully confirmed a bipolar S-shaped negative differential resistance (NDR) characteristics on a certain range of sheet-carrier concentration of the δp⁺ gate layer. Clear latch characteristics in the input-light power vs. current characteristics were also obtained in both the positive and negative biased conditions. We found that it is very important to optimize the sheet-carrier concentration to fabricate the S-TOPS.