Figure 1

Figure 2
![Cross-sectional TEM image of an over-etched substrate (containing oxidized [white]) and residual [light gray] AlGaN) by selective etching between p-GaN and AlGaN (top) and element distribution in the over-etched substrate generated from the EDS line scan (bottom).](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/685edb43e88a4c302353b87c/j_msp-2025-0025_fig_002.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKMAP2UW6E%2F20260119%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20260119T072558Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEMb%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJIMEYCIQD42JIMT8FAkobAIft8qXE7Dup4%2BALRgUXnp1nABKso2QIhAMvKxnZe8Z%2BaUePUHSy%2F8KVI8KVzB773Jyae8lXtQ%2BIyKsQFCI%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQAhoMOTYzMTM0Mjg5OTQwIgztCVp8fKC3iJBD4pUqmAWgtkgQ8Q2yfPrG131tbxAVS5mXrikAgdyD5hdYgLlVJyDKGmvhZW6%2BOh3EOJOOsfN48ynOPmglm8OZNY%2Fgj1%2FC%2BIb5swPG3lgLthd3dWPphNT5xqdEzkI2ILrW4xxfrkyUHdBU4OxPt4mAgidHlw3EHzY8FdjdPYNs2KxGSsWMKUrxcGTZFPJ3ezD89wIIl1oajJTITKLXmwJNooQWSYLlnsJYPvuCbQdYmCq1YcWQgIwlAdADKmsFNlbuOGXqF7R7bi8liuM5KCox5FaNA0af269mdILvqw4zXDFsI0KDlsCwIOk88MUBqGRJuLVNVNTihpUo0qG5J08MxNRyOa7iXRFBBnoqabQlX%2BNfkOXlqBo2WhFJ5uLqCZNbjJ3WhkXKrwbX2gbz53pSKKBYnQKHG%2BJkIYaLNhb3LkNhR64EYnI9YmVRXsmHhuxoaCcCSR8rp%2BZAGRmxgF78c2n9jUH2vt3BflbQx9FfPwTukrku8JIxMK0cmr2I%2B9RZ0kgQed9iqa3WGYd%2BuxSUY9zKJuXVZ6GVF%2B7BF9sDsqBC4qcwMbFd7cZ4EC%2BFVVWfZ4S%2B2kfVW2jZt8B7ZSoqKA%2Fk2zRxhVCh3HpgDPoV8S3nA32LALfTkNOUa6m9Vg8OOog2p7ZZ0ZB4X%2FYg%2BGURleuf2Yi6HoHn%2F%2Fdulcin2eAnjsMcjkJu4UXD94s4n0aZAj0AceKBKaonT%2BhrI85hIN06h%2FLjiNa4hEZIJ3jkLGzkLz7fN%2FcmuVd8sR3zMJrAh30PrLU7HmySBYBILnRWsodrIyO9b%2BoxMc4Vu3wTK2d1ocrhid7WdrsNmGYGVvbLTLqM9quPbQYFijEOGdN7Mu3WJxVIA266KuVX%2BtsB2kl94H5keUu1EFZyoZs6MNWFt8sGOrABK9deoz%2BhGAVx50ZdPcGvLTfUA9el8SBSjaF30HYz%2BCOD96yOFz9E7GD8RtSgwI8ANNyL4aLVb17GWGixyAvpLXSMSbDFqZk%2BpZyWHwUbZg38qHtoiUOseTiOKkisdlcVxQF%2BvHJQiUFYW54PIAWR18Lc4GICQFKp09BmKHBD835pAdwkiunizEZU%2Fod%2BWVIqgayY8cnsUypy4wiQ5g%2BpUdm52urD6EFYQt3AQ0gIZ5E%3D&X-Amz-Signature=f4b7d09ef6e00bd4a77adf36957bf49094531ae86845ed012b14bae76b27e2ef&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Comparison of switching performance parameters with other E-mode GaN-based devices_
| References | I ON /I OFF | SS (mV/dec) | V th (V) |
|---|---|---|---|
| This work (w/PDA) | 109 | 71.26 | 1.05 |
| [19] | 105 | — | 2.40 |
| [28] | 109 | 116 | 0.70 |
| [29] | 106 | — | 0.50 |
| [30] | 109 | 95 | 0.30 |
| [31] | 104 | 205 | 0.49 |
| [32] | 108 | — | 1.10 |
Comparison of typical performance parameters among the three types of HEMTs_
| Parameters | Ohmic gate | MOS-HEMT (w/o PDA) | MOS-HEMT (w/PDA) |
|---|---|---|---|
| V th (V) | 0.81 | 1.15 | 1.05 |
| SS (mV/dec) | 75.61 | 89.79 | 71.26 |
| g m,max (mS/mm) | 76.64 | 40.33 | 18.33 |
| Field effect mobility (cm2/V s) | 684 | 153 | 71.4 |
| I ON /I OFF | 2.17 × 1011 | 2.48 × 108 | 5.64 × 109 |