In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2022-01, No. 29 ( 2022-07-07), p. 1282-1282
Abstract:
TCO gated InGaAs MOSFETs are demonstrated as a high responsivity and broadband short-wave infrared (SWIR) photodetector under front-side illumination (FSI). InGaAs MOSFET structures have many advantages for monolithic integration with optical communication devices with O, C, and L bands and Si-LSI. The TCO gated InGaAs MOSFETs were fabricated through the gate-last method as shown in Fig. (a) [1]. A 300-nm-thick p-type In 0.53 Ga 0.47 As layer was grown on an InP (001) wafer using MOCVD. After the deposition of a 10-nm-thick Al 2 O 3 protection layer by ALD, the InGaAs active region was defined by chemical wet etching for mesa isolation. For the formation of the source/drain region, Si ions were implanted with 2×10 14 cm -2 at 15 keV, followed by RTA at 450 °C for 10 min to achieve dopant activation. After splitting the Al 2 O 3 protection layer, a 10-nm-thick Al 2 O 3 gate oxide layer was deposited again. As TCO gate, Ce and H co-doped In 2 O 3 (In 2 O 3 : Ce, H) with an electron mobility of ~160 cm 2 /V·s and a carrier density of ~ 2×10 20 cm -3 were used [2, 3]. The amorphous TCO gate, which were deposited onto the Al 2 O 3 layer using the ion plating method, were lifted off and crystallized by annealing at 250 °C for 30 min. Finally, Ti/Au formed for the S/D and gate contact after post-metallization annealing (PMA) at 250 °C for 30 min. The thin TCO films exhibited a very low specific contact resistance of 9.01 × 10 -8 W·cm 2 and a sheet resistance of 18.7W/sq. We confirmed the normal n-channel MOSFET operation with an I on / I off ratio of 〉 1×10 4 . S.S. and D it values were 134 mV/dec. and 5.2 × 10 12 eV -1 cm -2 , respectively. The peak G m was observed at V G = 0.5 V, and the extracted peak field-effect mobility was 620 cm 2 /V·s. The threshold voltage negatively shifted to -0.38 V, operating in enhancement mode owing to the work function of the TCO (4.2 eV), which is smaller than the Fermi level energy of p-type InGaAs (5.09 eV). Figure (b) shows the I D - V G characteristics of InGaAs MOSFETs at V G = 1 V in the dark and under illumination at the excitation wavelength of 1550 nm with an incident optical power of 5213 nW. SWIR light was illuminated in the channel area (L/W = 10 μm/10 μm) of TCO gated InGaAs MOSFET with a spot size of 10 μm. Under SWIR illumination, an increase in can be observed in the entire gate bias. Owing to the normally-on operation of the TCO gated InGaAs MOSFET, a photocurrent is detected even if the gate bias is 0 V. The photocurrent increased with the gate bias and reached the maximum in the vicinity of V G = 0.5 V, which corresponds to that of the maximum transconductance. The primary photo-response when the device is under illumination is known as the photovoltaic effect [4, 5]. The photo-generated holes move to the source region and accumulate at the potential barrier between the source and the channel. This results in the effective reduction of a potential barrier for electrons at the source edge. These phenomena lead to a decline in the threshold voltage of the MOSFET, which leads to the increase of the drain current. The threshold voltage of the TCO gated InGaAs MOSFETs in the dark was -0.35 V, and this value shifted to -0.45 V under illumination. Because is proportional to the mobility at the MOS interface, the improvement of the interface quality of the TCO/Al 2 O 3 /InGaAs MOS structures can enhance the sensitivity. Owing to the SWIR transparent TCO, we observed a responsivity of more than 1 A/W in the range of 1000 nm to 1800 nm, which includes the entire optical communication wavelength bands (1260–1625 nm). Because the maximum sensitivity of InGaAs photodiode was approximately 1 A/W at approximately 1550 nm [6], it is demonstrated that TCO gated InGaAs MOSFETs is a highly sensitive device in the SWIR region owing to the gain mechanism in the photoFETs. [1] T. Maeda, et al., Appl. Phys. Lett., 119, 192101 (2021). [2] T. Koida, et al., Status Solidi A, 215, 1700506 (2018). [3] T. Koida, et al., Status Solidi A, 218, 2000487 (2021). [5] Y. Takanashi, et al., IEEE Electro. Dev. Lett., 19, 472 (1998). [6] http://www.thorlabs.com . Figure 1
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2022-01291282mtgabs
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2022
detail.hit.zdb_id:
2438749-6
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