I am trying to save my custom field data through plugin but it's not working.

Plugin Class

namespace Vendor\Module\Model\Checkout;

class PaymentInformationManagementPlugin {

    protected $paymentMethodManagement;

    public function __construct(
        \Magento\Quote\Model\QuoteFactory $quote, 
        \Magento\Quote\Api\PaymentMethodManagementInterface $paymentMethodManagement
    ) {
        $this->paymentMethodManagement = $paymentMethodManagement;
        $this->quoteManagement = $quoteManagement;
    }    

    public function beforeSavePaymentInformation(
        \Magento\Checkout\Model\PaymentInformationManagement $subject, 
$cartId, 
        \Magento\Quote\Api\Data\PaymentInterface $paymentInformation
    ) {
        //$paymentInformation->getData('extension_attributes');
        $extenstinAttributes = $paymentInformation->getExtensionAttributes();
        $taxCode = $extenstinAttributes->getTaxCode();

        $paymentInformation->setExtensionAttributes($taxCode);
        $this->paymentMethodManagement->set($cartId, $paymentInformation);

        return true;
//        var_dump($taxCode);exit;
//        $quote=$this->quote->create();
//        $quote->getPayment()->setData('tax_code',$taxCode);
//        return $paymentInformation;
    }

}

extenstion_attribute.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="Magento\Quote\Api\Data\PaymentInterface">
        <attribute code="tax_code" type="string"/>
    </extension_attributes>
</config>

di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Checkout\Model\PaymentInformationManagement">
        <plugin name="save-in-quote-payment" type="Vendor\Module\Model\Checkout\PaymentInformationManagementPlugin" sortOrder="12349"/>
    </type>
</config>

Can anyone please help me on this.