Photoreflectance and Raman Study of Surface Electric States on AlGaAs/GaAs Heterostructures

<table class="table-group" id="tab1"><tr><td><table class="table"><tr><td class="thead-hr" colspan="5"><hr/></td></tr><tr class="thead"><td class="align_left">Sample</td><td class="align_center">Cap (nm)</td><td class="align_center">Si (ML)</td><td class="align_center"><svg height="11.927pt" id="M31" style="vertical-align:-3.291101pt" version="1.1" viewbox="-0.0498162 -8.6359 10.8893 11.927" width="10.8893pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M584 650H137L131 622C214 614 217 612 200 521L125 127C109 41 101 35 23 28L17 0H288L294 28C201 35 193 42 209 128L242 309H348C440 309 442 300 443 226H471L510 422H482C452 354 449 348 357 348H251L295 575C302 609 304 615 338 615H426C502 615 517 604 526 581C534 560 536 524 537 492L565 494C574 554 583 631 584 650Z" id="g113-71"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="607" vert-adv-y="607"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,6.786,3.132)"><path d="M357 391C357 416 325 451 270 451C241 451 179 431 146 400C109 365 97 334 97 307C97 248 143 213 196 180C250 146 261 123 261 101C261 75 237 40 190 40C153 40 110 72 86 109C81 116 68 119 55 112C37 102 24 87 24 66C24 30 85 -12 137 -12C229 -12 331 62 331 140C331 189 304 218 236 260C197 284 164 309 164 346C164 381 194 400 220 400C259 400 282 380 304 350C310 342 321 339 330 344C347 353 357 372 357 391Z" id="g50-116"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="381" vert-adv-y="381"></glyph.data></g></svg> (10<sup>7</sup> V/m)</td><td class="align_center"><svg height="12.0366pt" id="M32" style="vertical-align:-3.400701pt" version="1.1" viewbox="-0.0498162 -8.6359 15.9209 12.0366" width="15.9209pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M405 650H141L135 622C222 616 230 610 215 535L133 116C118 41 113 33 29 28L23 0H289L295 28C209 33 205 40 219 116L298 535C312 609 317 616 399 622L405 650Z" id="g113-74"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="428" vert-adv-y="428"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,4.719,3.132)"><path d="M499 166C484 119 466 88 447 68C424 43 390 38 338 38C297 38 262 40 242 51C223 62 218 80 218 133V522C218 607 226 612 309 617V650H41V617C124 612 131 605 131 522V129C131 45 123 38 38 33V0H497C505 30 529 128 534 160L499 166Z" id="g58-74"></path><glyph.data ascent="1007" descent="-369" horiz-adv-x="548" vert-adv-y="548"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,9.706,3.132)"><path d="M556 236V289H56V236H556Z" id="g54-33"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="611" vert-adv-y="611"></glyph.data></g></svg>/<svg height="11.9316pt" id="M33" style="vertical-align:-3.2957pt" version="1.1" viewbox="-0.0498162 -8.6359 17.1722 11.9316" width="17.1722pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M405 650H141L135 622C222 616 230 610 215 535L133 116C118 41 113 33 29 28L23 0H289L295 28C209 33 205 40 219 116L298 535C312 609 317 616 399 622L405 650Z" id="g113-74"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="428" vert-adv-y="428"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,4.719,3.132)"><path d="M499 166C484 119 466 88 447 68C424 43 390 38 338 38C297 38 262 40 242 51C223 62 218 80 218 133V522C218 607 226 612 309 617V650H41V617C124 612 131 605 131 522V129C131 45 123 38 38 33V0H497C505 30 529 128 534 160L499 166Z" id="g58-74"></path><glyph.data ascent="1007" descent="-369" horiz-adv-x="548" vert-adv-y="548"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,9.624,3.132)"><path d="M387 665C175 665 46 498 46 318C46 123 194 -15 374 -15C558 -15 712 114 712 333C712 535 557 665 387 665ZM364 625C495 625 607 518 607 306C607 115 505 25 396 25C256 25 151 161 151 346C151 532 255 625 364 625Z" id="g58-77"></path><glyph.data ascent="1007" descent="-369" horiz-adv-x="757" vert-adv-y="757"></glyph.data></g></svg></td></tr><tr><td class="thead-hr" colspan="5"><hr/></td></tr><tr><td class="align_left">M1</td><td class="align_center">25</td><td class="align_center">0</td><td class="align_center">5.99</td><td class="align_center">0.1699</td></tr><tr><td class="align_left">M2</td><td class="align_center">60</td><td class="align_center">0</td><td class="align_center">3.57</td><td class="align_center">0.1407</td></tr><tr><td class="align_left">M3</td><td class="align_center">80</td><td class="align_center">0</td><td class="align_center">3.40</td><td class="align_center">0.1345</td></tr><tr><td class="align_left">M4</td><td class="align_center">25</td><td class="align_center">1</td><td class="align_center">5.91</td><td class="align_center">0.1896</td></tr><tr><td class="align_left">M5</td><td class="align_center">25</td><td class="align_center">2</td><td class="align_center">5.08</td><td class="align_center">0.1772</td></tr><tr class="table-tr"><td colspan="5"><hr class="tbody-hr"/></td></tr></table></td></tr></table>

Cap layer thickness, surface electric field (<svg height="11.927pt" id="M28" style="vertical-align:-3.291101pt" version="1.1" viewbox="-0.0498162 -8.6359 10.8893 11.927" width="10.8893pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M584 650H137L131 622C214 614 217 612 200 521L125 127C109 41 101 35 23 28L17 0H288L294 28C201 35 193 42 209 128L242 309H348C440 309 442 300 443 226H471L510 422H482C452 354 449 348 357 348H251L295 575C302 609 304 615 338 615H426C502 615 517 604 526 581C534 560 536 524 537 492L565 494C574 554 583 631 584 650Z" id="g113-71"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="607" vert-adv-y="607"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,6.786,3.132)"><path d="M357 391C357 416 325 451 270 451C241 451 179 431 146 400C109 365 97 334 97 307C97 248 143 213 196 180C250 146 261 123 261 101C261 75 237 40 190 40C153 40 110 72 86 109C81 116 68 119 55 112C37 102 24 87 24 66C24 30 85 -12 137 -12C229 -12 331 62 331 140C331 189 304 218 236 260C197 284 164 309 164 346C164 381 194 400 220 400C259 400 282 380 304 350C310 342 321 339 330 344C347 353 357 372 357 391Z" id="g50-116"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="381" vert-adv-y="381"></glyph.data></g></svg>) obtained from PR measurements, and <svg height="12.0366pt" id="M29" style="vertical-align:-3.400701pt" version="1.1" viewbox="-0.0498162 -8.6359 15.9209 12.0366" width="15.9209pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M405 650H141L135 622C222 616 230 610 215 535L133 116C118 41 113 33 29 28L23 0H289L295 28C209 33 205 40 219 116L298 535C312 609 317 616 399 622L405 650Z" id="g113-74"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="428" vert-adv-y="428"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,4.719,3.132)"><path d="M499 166C484 119 466 88 447 68C424 43 390 38 338 38C297 38 262 40 242 51C223 62 218 80 218 133V522C218 607 226 612 309 617V650H41V617C124 612 131 605 131 522V129C131 45 123 38 38 33V0H497C505 30 529 128 534 160L499 166Z" id="g58-74"></path><glyph.data ascent="1007" descent="-369" horiz-adv-x="548" vert-adv-y="548"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,9.706,3.132)"><path d="M556 236V289H56V236H556Z" id="g54-33"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="611" vert-adv-y="611"></glyph.data></g></svg>/<svg height="11.9316pt" id="M30" style="vertical-align:-3.2957pt" version="1.1" viewbox="-0.0498162 -8.6359 17.1722 11.9316" width="17.1722pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M405 650H141L135 622C222 616 230 610 215 535L133 116C118 41 113 33 29 28L23 0H289L295 28C209 33 205 40 219 116L298 535C312 609 317 616 399 622L405 650Z" id="g113-74"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="428" vert-adv-y="428"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,4.719,3.132)"><path d="M499 166C484 119 466 88 447 68C424 43 390 38 338 38C297 38 262 40 242 51C223 62 218 80 218 133V522C218 607 226 612 309 617V650H41V617C124 612 131 605 131 522V129C131 45 123 38 38 33V0H497C505 30 529 128 534 160L499 166Z" id="g58-74"></path><glyph.data ascent="1007" descent="-369" horiz-adv-x="548" vert-adv-y="548"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,9.624,3.132)"><path d="M387 665C175 665 46 498 46 318C46 123 194 -15 374 -15C558 -15 712 114 712 333C712 535 557 665 387 665ZM364 625C495 625 607 518 607 306C607 115 505 25 396 25C256 25 151 161 151 346C151 532 255 625 364 625Z" id="g58-77"></path><glyph.data ascent="1007" descent="-369" horiz-adv-x="757" vert-adv-y="757"></glyph.data></g></svg> ratio calculated from Raman measurements. 

Journal of Spectroscopy

tab1

Table 1

Table 1: Photoreflectance and Raman Study of Surface Electric States on AlGaAs/GaAs Heterostructures 