Create a entity basefield with an entity reference type #drupal8

basefield_entityreference.php

$fields['physical_location'] = BaseFieldDefinition::create('entity_reference')->setLabel(t('Physical Location'))
    ->setDescription(t('Reference the idenfication number of a physical location'))
    ->setRevisionable(FALSE)
    ->setSetting('target_type', 'site_entity')
    ->setSetting('handler', 'default')
    ->setTranslatable(FALSE)
    ->setDisplayOptions('form', [
        'type' => 'entity_reference_autocomplete',
        'settings' => [
            'match_operator' => 'CONTAINS',
            'size' => 50,
            'placeholder' => t('Enter identification number of label'),
        ],
    ])
    ->setDisplayOptions('view', [
        'label' => t("Physical Location"),
        'type' => 'string',
    ])
    ->setDisplayConfigurable('form', TRUE)
    ->setDisplayConfigurable('view', TRUE);