Valence and conduction band offsets in AZO/Ga2O3 heterostructures

Abstract

We report on the determination of band offsets in rf-sputtered Aluminum Zinc Oxide (AZO)/single crystal β-Ga 2 O 3 (AZO/Ga 2 O 3) heterostructures using X-Ray Photoelectron Spectroscopy. The bandgaps of the materials were determined by Reflection Electron Energy Loss Spectroscopy as 4.6 eV for Ga 2 O 3 and 3.2eV for AZO. The valence band offset was determined to be-0.61eV ± 0.23eV, while the conduction band offset was determined to be-0.79 ± 0.34 eV. The AZO/Ga 2 O 3 system has a nested, or straddling, gap (type I) alignment and provides a convenient method for reducing contact resistance on Ga 2 O 3-based device structures.

Investigation of Energy Band at Atomic-Layer-Deposited ZnO/β-Ga2O3 ( 2 ¯ 01 $$ \overline{2}01 $$ ) Heterojunctions

“…Figure 2a presents the CL spectra of Zn 2p on the ZnO (40 nm)/β-Ga 2 O 3 , which is quiet symmetrical indicating the uniform bonding state, and the peak locates at 1021.09 eV corresponds the Zn-O bond [25]. The VBM can be determined using a linear extrapolation method [26]. The VBM of ZnO is located at 2.11 eV.…”

Valence and Conduction Band Offsets for InN and III-Nitride Ternary Alloys on (−201) Bulk β-Ga2O3

“…40 In fact, our measured valence band offset for InN was similar to the the theoretical valence band offset for In 2 O 3 /Ga 2 O 3 , as recently reported by Swallow et al 41 It is worth pointing out that measured valence bands for AlN and Al 2 O 3 , deposited by ALD on (−201) β-Ga 2 O 3 by two different groups, were similar as well: −0.09 ± 0.1 eV for PEALD AlN and 0.07 ± 0.2 eV for ALD Al2O3. 17,31 While interfacial O was likely present in our films, preliminary depth-resolved XPS profiling did not indicate significant O content in our films, and as our growth substrate was an oxide the interfacial O content was impossible to quantify. We would reasonably expect the valence band offset for InN to Ga 2 O 3 in future reports to increase by up to about 1 eV as the effect of interfacial O is eliminated.…”

“…Band offsets have been reported for most relevant oxides on Ga 2 O 3 in search of candidate gate dielectrics for ultra-wide bandgap electronics. [16][17][18][19][20][21][22][23][24][25][26] In addition, common semiconductor heterojunctions have been reported as well, including Si, SiC, GaN, AlN, and IZGO. [27][28][29][30][31][32] Measuring band offsets for the InN/β-Ga 2 O 3 heterojunction is thus complementary to the reported results for the other III-Nitride materials AlN and GaN.…”

Ohmic contacts on n-type β-Ga2O3 using AZO/Ti/Au

“…33 The bandgaps of the component materials were 4.6 eV for Ga 2 O 3 and 3.2 eV for AZO, with AZO/Ga 2 O 3 system having a nested gap (type I) alignment, as shown in Figure 2. Thus, use of a thin layer of AZO has the ability to reduce the barrier for electron transport and hence the contact resistance between the metal and Ga 2 O 3 .…”