Vertical Current Transport in AlGaN/GaN HEMTs on Silicon: Experimental Investigation and Analytical Model

• Published in: IEEE transactions on electron devices 2019-01, Vol.66 (1), p.613-618
• Main Authors: Remesh, Nayana, Mohan, Nagaboopathy, Kumar, Sandeep, Prabhu, Shreesha, Guiney, Ivor, Humphreys, Colin J., Raghavan, Srinivasan, Muralidharan, Rangarajan, Nath, Digbijoy N.
• Format: Article
• Language: English
• Subjects: 2-D electron gas; Activation energy; AlGaN; Aluminum gallium nitride; Aluminum gallium nitrides; Buffers; Complex formation; Dislocation density; Electron mobility; Gallium nitride; Gallium nitrides; HEMTs; High electron mobility transistors; high-electron mobility transistor (HEMT); hopping conduction; Leakage; Mathematical models; Metalorganic chemical vapor deposition; MODFETs; Organic chemicals; Organic chemistry; Point defects; Polarity; Poole–Frenkel (P–F); Semiconductor devices; Silicon; Silicon substrates; Silicon wafers; Temperature dependence; Temperature measurement; Transport; vertical leakage; Wide band gap semiconductors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2018.2882533

We investigate the vertical leakage mechanism in metal-organic chemical vapor deposition-grown carbon (C)-doped AlGaN/GaN High Electron Mobility Transistors (HEMTs) on 6-in silicon wafer. Substrate bias polarity-dependent {I} - {V}_{s} , temperature-dependent fitting, and band diagram analysis pointed to the Poole-Frenkel (P-F) type of conduction mechanism for vertical transport in the devices with breakdown as high as 580 V for a buffer of \textsf {4}~\mu \text{m} . Trap activation energy of 0.61 eV was estimated from the P-F fitting which matches well with values reported in the literature. We propose that higher dislocation density leads to shallower traps in the buffer and build an analytical model of dislocation-mediated vertical leakage around this. The variation in leakage as a function of dislocation density at a given field is predicted and is found to be the most abrupt in the range from \sim 10^{\textsf {7}} to \sim 10^{\textsf {9}} cm ^{-\textsf {2}} of dislocation density. This can be attributed to a sharp decrease in trap activation energy in the above range of dislocation density, possibly due to complex formation between point defects and dislocations.