Valence band engineering of GaAsBi for low noise avalanche photodiodes

Abstract

Avalanche Photodiodes (APDs) are key semiconductor components that amplify weak optical signals via the impact ionization process, but this process’ stochastic nature introduces ‘excess’ noise, limiting the useful signal to noise ratio (or sensitivity) that is practically achievable. The APD material’s electron and hole ionization coefficients (α and β respectively) are critical parameters in this regard, with very disparate values of α and β necessary to minimize this excess noise. Here, the analysis of thirteen complementary p-i-n/n-i-p diodes shows that alloying GaAs with ≤ 5.1 % Bi dramatically reduces β while leaving α virtually unchanged—enabling a 2 to 100-fold enhancement of the GaAs α/β ratio while extending the wavelength beyond 1.1 µm. Such a dramatic change in only β is unseen in any other dilute alloy and is attributed to the Bi-induced increase of the spin-orbit splitting energy (∆so). Valence band engineering in this way offers an attractive route to enable low noise semiconductor APDs to be developed.

Avalanche multiplication and excess noise characteristics in antimony-based avalanche photodiodes

“…The mechanism responsible for the low excess noise in some of these Sb containing alloys may be due in part to the large size of the Sb atom. Recent work by Liu et al [31] on the ionization coefficients in GaAsBi alloys showed that as the Bi content increases, the band-anticrossing interaction in the valence band increases the spin-orbit splitting energy (△ so ) [31]. Holes in the heavy/light hole bands now reach the Brillouin zone edge and may not be able to scatter into the split-off band from which hole ionization is mainly initiated.…”

GaAsBi: From Molecular Beam Epitaxy Growth to Devices

“…In 2021, Liu et al reported on the avalanche multiplication properties of a series of GaAsBi p-i-n and n-i-p diodes of various Bi contents and thicknesses. [38] They found that the enhanced spin-orbit splitting of GaAsBi prevented holes from accessing the split-off band and attaining the energies necessary to initiate impact ionisation. The result was that the hole ionisation coefficient in GaAsBi dropped dramatically with increasing Bi content, while the electron ionisation coefficient was left almost unaltered.…”

Manipulating Surface Band Bending of III‐Nitride Nanowires with Ambipolar Charge‐Transfer Characteristics: A Pathway Toward Advanced Photoswitching Logic Gates and Encrypted Optical Communication

“…[1][2][3] While band structure engineering has been proven to be the most powerful strategy to control charge-transfer characteristics in semiconductor devices. [4][5][6] Typically, the common approach to adjusting the band structure of materials is often carried out in the synthesis stage by varying the chemical doping, [7,8] controlling the composition of alloys (binary, ternary, or quaternary), [9,10] or constructing heterojunctions. [11][12][13] Alternatively, band structure engineering can also be realized by externally modulating in the postsynthesis stage by changing the surrounding environment including introducing a strong electrical/optical/magnetic field, [14][15][16] applying stress-strain strategies to tune crystal sizes/shapes, [17][18][19] or surface decoration and optimization.…”