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Room temperature electrically tunable rectification magnetoresistance in Ge-based Schottky devices

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ABSTRACT

Electrical control of magnetotransport properties is crucial for device applications in the field of spintronics. In this work, as an extension of our previous observation of rectification magnetoresistance, an innovative technique for electrical control of rectification magnetoresistance has been developed by applying direct current and alternating current simultaneously to the Ge-based Schottky devices, where the rectification magnetoresistance could be remarkably tuned in a wide range. Moreover, the interface and bulk contribution to the magnetotransport properties has been effectively separated based on the rectification magnetoresistance effect. The state-of-the-art electrical manipulation technique could be adapt to other similar heterojunctions, where fascinating rectification magnetoresistance is worthy of expectation.

No MeSH data available.


Transport measurements of devices grown on different substrates.(a)–(c) respectively show the corresponding I-V curves in different magnetic field (a), conventional DC MR (b), and AC rectification MR (c) for the intrinsic Ge-Schottky devices and Ge substrates. In (b) and (c), the bulk properties (marked by bulk) of the intrinsic Ge substrate have been measured after changing the Schottky electrode into Ohmic contact, where linear I-V curves have been confirmed as shown in the inset of (a). In (b), the interface DC voltage is obtained by subtracting the bulk signal from the total signal. In (c), the interface DC voltage of Ge-Schottky devices is directly measured under AC current. (d)–(f) are the same measurements as (a)–(c), but for the p-type Ge-Schottky devices and Ge substrates. (g)–(i) are also the same measurements as (a)–(c), but for the n-type Ge-Schottky devices and Ge substrates.
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f2: Transport measurements of devices grown on different substrates.(a)–(c) respectively show the corresponding I-V curves in different magnetic field (a), conventional DC MR (b), and AC rectification MR (c) for the intrinsic Ge-Schottky devices and Ge substrates. In (b) and (c), the bulk properties (marked by bulk) of the intrinsic Ge substrate have been measured after changing the Schottky electrode into Ohmic contact, where linear I-V curves have been confirmed as shown in the inset of (a). In (b), the interface DC voltage is obtained by subtracting the bulk signal from the total signal. In (c), the interface DC voltage of Ge-Schottky devices is directly measured under AC current. (d)–(f) are the same measurements as (a)–(c), but for the p-type Ge-Schottky devices and Ge substrates. (g)–(i) are also the same measurements as (a)–(c), but for the n-type Ge-Schottky devices and Ge substrates.

Mentions: In order to go one step further towards a practical application of the rectification MR effect, the contributions from bulk layer as well as the interface to the magnetotransport properties have been separated by utilizing the interfacial nature of the rectification MR. Three types of Ge substrates with different resistivity has been used. The asymmetric I-V curves (Fig. 2a,d and g) were observed in all the as-prepared devices, indicating the existence of Schottky interfaces. As clearly shown in Fig. 2c,f and i, no rectification MR is observed after destroying the Schottky contact, meaning that bulk Ge substrate could not contribute to the rectification MR regardless its large difference in the resistivity. Rectification MR is only observed in p-type Ge-Schottky and intrinsic Ge-Schottky devices with much higher resistivity, suggesting that low carrier concentration is beneficial for the observation of rectification MR. This is consistent with previous report that shrinkage of carrier wave function under magnetic field is the physical origin of rectification MR1828. Returning to the conventional DC magnetoresistance effect, it is reasonable to believe that the conventional DC voltages measured at the as-prepared Ge-Schottky devices (marked as total) contains the contribution from both the Schottky interface and the bulk Ge. After changing the Schottky contact into Ohmic contact, only the bulk signals could be measured as shown in Fig. 2b,e and h (marked as bulk). As a result, the interfacial contributions (marked as interface) to the conventional MR could be deduced by deducting the bulk signals from the total signals, assuming that bulk and interfacial resistance formed an equivalent series circuit. A linear magnetic field dependence of the interfacial conventional MR is obtained, suggesting that same physics lies behind the MR of both the interface and bulk components. In such a way, the interface and bulk contributions to the magnetotransport could be effectively separated by combing measurements under DC and AC. It should be pointed out that the positive conventional MR observed in n-type Ge (Fig. 2h) has a negligible influence on the interfacial MR (both total MR and interface MR is nearly zero), because its resistance is too small as compared with that of the Schottky interface.


Room temperature electrically tunable rectification magnetoresistance in Ge-based Schottky devices
Transport measurements of devices grown on different substrates.(a)–(c) respectively show the corresponding I-V curves in different magnetic field (a), conventional DC MR (b), and AC rectification MR (c) for the intrinsic Ge-Schottky devices and Ge substrates. In (b) and (c), the bulk properties (marked by bulk) of the intrinsic Ge substrate have been measured after changing the Schottky electrode into Ohmic contact, where linear I-V curves have been confirmed as shown in the inset of (a). In (b), the interface DC voltage is obtained by subtracting the bulk signal from the total signal. In (c), the interface DC voltage of Ge-Schottky devices is directly measured under AC current. (d)–(f) are the same measurements as (a)–(c), but for the p-type Ge-Schottky devices and Ge substrates. (g)–(i) are also the same measurements as (a)–(c), but for the n-type Ge-Schottky devices and Ge substrates.
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Related In: Results  -  Collection

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f2: Transport measurements of devices grown on different substrates.(a)–(c) respectively show the corresponding I-V curves in different magnetic field (a), conventional DC MR (b), and AC rectification MR (c) for the intrinsic Ge-Schottky devices and Ge substrates. In (b) and (c), the bulk properties (marked by bulk) of the intrinsic Ge substrate have been measured after changing the Schottky electrode into Ohmic contact, where linear I-V curves have been confirmed as shown in the inset of (a). In (b), the interface DC voltage is obtained by subtracting the bulk signal from the total signal. In (c), the interface DC voltage of Ge-Schottky devices is directly measured under AC current. (d)–(f) are the same measurements as (a)–(c), but for the p-type Ge-Schottky devices and Ge substrates. (g)–(i) are also the same measurements as (a)–(c), but for the n-type Ge-Schottky devices and Ge substrates.
Mentions: In order to go one step further towards a practical application of the rectification MR effect, the contributions from bulk layer as well as the interface to the magnetotransport properties have been separated by utilizing the interfacial nature of the rectification MR. Three types of Ge substrates with different resistivity has been used. The asymmetric I-V curves (Fig. 2a,d and g) were observed in all the as-prepared devices, indicating the existence of Schottky interfaces. As clearly shown in Fig. 2c,f and i, no rectification MR is observed after destroying the Schottky contact, meaning that bulk Ge substrate could not contribute to the rectification MR regardless its large difference in the resistivity. Rectification MR is only observed in p-type Ge-Schottky and intrinsic Ge-Schottky devices with much higher resistivity, suggesting that low carrier concentration is beneficial for the observation of rectification MR. This is consistent with previous report that shrinkage of carrier wave function under magnetic field is the physical origin of rectification MR1828. Returning to the conventional DC magnetoresistance effect, it is reasonable to believe that the conventional DC voltages measured at the as-prepared Ge-Schottky devices (marked as total) contains the contribution from both the Schottky interface and the bulk Ge. After changing the Schottky contact into Ohmic contact, only the bulk signals could be measured as shown in Fig. 2b,e and h (marked as bulk). As a result, the interfacial contributions (marked as interface) to the conventional MR could be deduced by deducting the bulk signals from the total signals, assuming that bulk and interfacial resistance formed an equivalent series circuit. A linear magnetic field dependence of the interfacial conventional MR is obtained, suggesting that same physics lies behind the MR of both the interface and bulk components. In such a way, the interface and bulk contributions to the magnetotransport could be effectively separated by combing measurements under DC and AC. It should be pointed out that the positive conventional MR observed in n-type Ge (Fig. 2h) has a negligible influence on the interfacial MR (both total MR and interface MR is nearly zero), because its resistance is too small as compared with that of the Schottky interface.

View Article: PubMed Central - PubMed

ABSTRACT

Electrical control of magnetotransport properties is crucial for device applications in the field of spintronics. In this work, as an extension of our previous observation of rectification magnetoresistance, an innovative technique for electrical control of rectification magnetoresistance has been developed by applying direct current and alternating current simultaneously to the Ge-based Schottky devices, where the rectification magnetoresistance could be remarkably tuned in a wide range. Moreover, the interface and bulk contribution to the magnetotransport properties has been effectively separated based on the rectification magnetoresistance effect. The state-of-the-art electrical manipulation technique could be adapt to other similar heterojunctions, where fascinating rectification magnetoresistance is worthy of expectation.

No MeSH data available.