Triangular-barrier optoelectronic switch by gas source molecular beam epitaxy

We report a novel optical functional device, triangular-barrier optoelectronic switch (TOPS), which consists of a triangular-barrier phototransistor (TBP) with avalanche multiplication, grown by gas source molecular beam epitaxy (GSMBE). At first we fabricated and examined the TBP, which was composed of In_0.53Ga_0.47As/In_0.52Al_0.48As layers to confirm its fundamental characteristics such as high sensitivity. On this basis, we optimized the structure, mainly about a δp⁺ gate layer, to introduce avalanche multiplication at low bias voltages into the TBP. We examined the characteristics of the TOPS with an input light of 1.55 μm wavelength. We observed significant S-shaped negative differential resistance (NDR) characteristics. Clear differential gain, bistability and latch characteristics were obtained by only changing the bias voltages, while the input-light power was less than 600 nW and the optical gain was more than 7000. We also found that it is very important to optimize the thickness of the gate layer to fabricate the TOPS. We can apply the TOPS to optical functional devices such as an optical logic device and an optical memory.