Nondestructive imaging of buried interfaces in SiC and GaN Schottky contacts using scanning internal photoemission microscopy

Shiojima, Kenji; Yamamoto, Shingo; Kihara, Yuhei; Mishima, Tomoyoshi

doi:10.7567/apex.8.046502

Cited by 27 publications

(24 citation statements)

References 25 publications

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“…For top-contacted 2D devices, there have been reports on non-destructive imaging and characterization of contact regions by using thermal nanolithography [192] and of buried interfaces by using scanning probe techniques. [193,194] However, nondestructive scanning probe techniques for 1D edge contacts need to be developed since the probing on 1D contact interface cannot be done from the top or bottom of the edge-contacted devices, being different from the top-contacted devices.…”

Section: Challenges Of Edge Contactmentioning

confidence: 99%

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

et al. 2022

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It is therefore becoming increasingly important to analyze the electronic properties of nanometer scale semiconductors from the quantum mechanical perspective. Due to their atomic thickness, 2D materials (2DMs) are considered to be the best candidates for revealing the quantum mechanical properties when used as semiconducting channel materials in electronic devices, thus representing alternatives to the conventional semiconducting materials such as Si and GaAs. [1] However, the use of 2DMs leads to large contact resistance (R C ) when they are in contact with metallic electrodes, since they form a metallic interface that depends on van der Waals (vdW) bonding, which induces the vdW gap and generates metalinduced gap states, ultimately resulting in Fermi-level pinning (FLP). [2,3] As a result, the electronic mobility of the metal-contacted 2DM based devices is found to be much lower than the theoretically expected value, thus preventing their quantum properties from being observed. Therefore, minimizing the R C of the devices using 2DMs represents the most important challenge for exploring the novel quantum electronic properties of the devices. In this regard, there have been substantial efforts to reduce the R C by using novel contact strategies. [4,5] Clean vdW contacts either by transferring metal/ semimetal electrodes or depositing indium on 2D semiconductors have been proposed to obtain high-quality metal-semiconductor (MS) interfaces without generating metallization induced defects. [6][7][8][9][10][11] High density doping achieved by chemical dopants, substitutional doping, solid oxides, and semimetals has also been utilized to reduce the R C significantly. [12][13][14][15][16][17][18][19][20] However, such contacts were typically placed onto the vdW surface of 2D semiconductors resulting in the formation of vdW tunneling barriers as well as the limitation in lateral scaling of the devices. Here, the 1D edge contact methods have been studied intensively as a very suitable technique for achieving a vdW gap-free electrical contact in scaled 2D devices.Edge-contacted 2D devices were first demonstrated for the purpose of suppressing scattering from the surface of 2DMs by encapsulating graphene with 2D hBN. [21] Following this initial report, the 1D edge contact method became more widely employed due to its additional advantages in the operation of 2D devices: the realization of Fermi-level depinning Recent studies have intensively examined 2D materials (2DMs) as promising materials for use in future quantum devices due to their atomic thinness. However, a major limitation occurs when 2DMs are in contact with metals: a van der Waals (vdW) gap is generated at the 2DM-metal interfaces, which induces metal-induced gap states that are responsible for an uncontrollable Schottky barrier (SB), Fermi-level pinning (FLP), and high contact resistance (R C ), thereby substantially lowering the electronic mobility of 2DMbased devices. Here, vdW-gap-free 1D edge contact is reviewed for use in 2D devices with substantially su...

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Section: Challenges Of Edge Contactmentioning

confidence: 99%

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

et al. 2022

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“…Therefore, in this study, we conducted two‐dimensional characterization of the effect of surface morphology on the electrical properties of low‐carrier thick n‐GaN layers via scanning internal photoemission microscopy (SIPM). SIPM was originally developed by the authors, which can visualize local variations in electrical characteristics of metal/semiconductor interfaces . Nanoscale, two‐dimensional characterization using a conductive atomic force microscope has been reported for Pt/GaN Schottky contacts .…”

Section: Introductionmentioning

confidence: 99%

“…SIPM was originally developed by the authors, which can visualize local variations in electrical characteristics of metal/ semiconductor interfaces. [17][18][19][20] Nanoscale, two-dimensional characterization using a conductive atomic force microscope has been reported for Pt/GaN Schottky contacts. [21] In contrast, SIPM can map the contacts through macroscopic observation.…”

Section: Introductionmentioning

confidence: 99%

Mapping of n‐GaN Schottky Contacts With Wavy Surface Morphology Using Scanning Internal Photoemission Microscopy

Shiojima

Hashizume

Horikiri

et al. 2017

Physica Status Solidi (b)

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We characterized the effects of surface morphology on the electrical properties of n‐GaN drift‐layers by using scanning internal photoemission microscopy (SIPM). We grew 12‐μm‐thick low carrier concentration (approximately 1 × 1016 cm−3) n‐GaN layers with both flat and wavy surface morphologies on freestanding GaN substrates by metal organic chemical vapor deposition. In the SIPM results, the samples with flat surfaces exhibited a uniform photocurrent distribution independently of the carrier concentration. In contrast, wavy patterns in the photocurrent maps were the same as the surface morphology for samples with low carrier concentration. These results indicate that the amount of C incorporated during the growth was affected by the off‐angle of the GaN surface, and the carrier compensation by C atoms was changed. We demonstrated that SIPM is a powerful tool for nondestructively visualizing the inhomogeneity of the carrier compensation over the wafers.

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“…We originally developed scanning internal photoemission microscopy (SIPM) to map electrical characteristics of metal/ semiconductor interfaces. 13,14) We have demonstrated the mapping of characteristics for interfacial reactions; degradation under applied voltage stress; and surface damage for Schottky contacts on Si, 13) GaAs, [14][15][16] GaN, [17][18][19][20][21] indiumgallium-zinc oxide, 22) and SiC. 17,[23][24][25] The advantage of this method is that local variation in the electrical characteristics can be clearly visualized.…”

Section: Introductionmentioning

confidence: 99%

Characterization of peripheries of n-GaN Schottky contacts using scanning internal photoemission microscopy

Imabayashi

Yasui²,

Horikiri³

et al. 2022

Jpn. J. Appl. Phys.

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We applied scanning internal photoemission microscopy (SIPM) to clarify the electrical characteristics on the electrode periphery of Ni/n-GaN Schottky contacts. Two types of Schottky contacts with different electrode formation methods were prepared. For the samples in which the Ni contacts were evaporated through a metal shadow mask, in the scanning electron microscopes (SEM) observation, the electrode edges were tailed and the tail was divided into two contrasts, a bright region with a width of 15.5-m from the electrode edge followed by a dark region with a width of 32-m. The SIPM signal was obtained from the first 16-m tailing region, and corresponded with the SEM images. For the photolithography sample, a sharp edge less than 1-m-wide was obtained and no increase in SIPM signal was detected on the edge. These results indicate SIPM is able to characterize the electrical properties of electrode periphery in conjunction with the structural characteristics.

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Nondestructive imaging of buried interfaces in SiC and GaN Schottky contacts using scanning internal photoemission microscopy

Cited by 27 publications

References 25 publications

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

Mapping of n‐GaN Schottky Contacts With Wavy Surface Morphology Using Scanning Internal Photoemission Microscopy

Characterization of peripheries of n-GaN Schottky contacts using scanning internal photoemission microscopy

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